---
title: Dev Chats - Extending Rails with Engines
slug: dev-chats-extending-rails-with-engines
published_at: 2022-08-18 10:13:32 +0000
updated_at: 2026-03-04 20:13:20 +0000
summary: 
description: Quite often, developers need to include some additional functionality to their application frameworks to improve code usability and their own productivity.  In this live session, Chris Oliver returns to join Cecil and CJ to talk about how Ruby on Rails developers can use Engines to extend the functionality of their applications.
tags: []
views: 467
author: CJ Avilla
url: https://www.cjav.dev/videos/dev-chats-extending-rails-with-engines
youtube_url: https://www.youtube.com/watch?v=5NxbmRVKuC0
youtube_id: 5NxbmRVKuC0
embed_url: https://www.youtube.com/embed/5NxbmRVKuC0
thumbnail_url: https://i.ytimg.com/vi/5NxbmRVKuC0/hqdefault.jpg
type: video
---

# Dev Chats - Extending Rails with Engines

*Published: August 18, 2022*
*Views: 467*

## Watch

[Watch on YouTube](https://www.youtube.com/watch?v=5NxbmRVKuC0)

[![Dev Chats - Extending Rails with Engines](https://i.ytimg.com/vi/5NxbmRVKuC0/hqdefault.jpg)](https://www.youtube.com/watch?v=5NxbmRVKuC0)

## Description

Quite often, developers need to include some additional functionality to their application frameworks to improve code usability and their own productivity.

In this live session, Chris Oliver returns to join Cecil and CJ to talk about how Ruby on Rails developers can use Engines to extend the functionality of their applications.

## Transcript

foreign [Music] [Music] [Music] [Music] foreign [Music] [Music] [Music] foreign [Music] [Music] [Music] foreign [Music] [Music] [Music] foreign [Music] [Music] [Music] [Music] foreign [Music] [Music] foreign [Music] [Music] [Music] [Music] foreign [Music] [Music] foreign [Music] [Music] and we&#39;re live hi everyone welcome to another stripe dab chats so the last time maybe not the last time like two streams ago we had Chris there and he was on he was talking to us about how he extended rails using this his Pig extension and showed us how he could you know accept payments inside of a ruby on Ariel&#39;s app and you know we got so much good feedback from it and I feel like the conversation wasn&#39;t done yet so we have to have him come back on and we&#39;re gonna die a little bit deeper we&#39;re gonna go under the covers a little bit and see well how exactly did he even make this extension and what are some of the things that you need to do if you want to make your own extension too so that&#39;s what we&#39;re going to talk about today we&#39;re going to talk about how you can extend rails using engines and I&#39;m super curious about it I&#39;m not a ruby person CJ I know you&#39;ve done a little bit of Ruby so maybe you might have more context than I do but again always interested to see you know like different communities and different Frameworks like so uh Chris why don&#39;t you like super quick again I know probably most folks already know who you are why don&#39;t you super quick just go ahead and introduce yourself again and let folks know who you are and what do you do sure uh I&#39;m Chris Oliver I run go rails uh hatchbox and jumpstart Pro and a bunch of Open Source gems um for Ruby on Rails developers make screencasts app templates with SAS templates um and hosting stuff so just kind of a wild variety of different Ruby on Rails related things so that&#39;s okay so I guess what you&#39;re saying is if I wanted to learn Ruby like you were the person that I should learn it from like that&#39;s that&#39;s what I&#39;m hearing right now hopefully yeah yeah we we have mostly rails related stuff but actually um we&#39;re gonna be doing uh some like beginner Ruby content and stuff like that too so um yeah plenty of plenty of things to learn if you there&#39;s like 450 some videos now on on go rails so it&#39;s a lot it&#39;s been a lot that&#39;s amazing okay so I want you to hold that thought because I want us to talk about it but before we do that I want to dive into some highlights you know we always try and do in the beginning of depth chats if this is your first time here we usually try and look at some of the cool things that have been happening in the community over the past year so let&#39;s do this super quick and then after that we can dive into uh into talking about engines all right so first thing I want to mention to folks so if you don&#39;t know we have a stripe developers Channel I know some of you all are watching us on YouTube but we&#39;re also on Twitch and I think we might be actually even on Twitter today we have a lot of different channels that we uh stream from but if you&#39;re watching and you still haven&#39;t subscribed to the channel I&#39;d love for you to do that we have tons of amazing videos and even specifically next month what&#39;s interesting is that we&#39;re going to do the entire month of September focused on something we have called checkout if you&#39;re not familiar check out in my opinion is one of the easiest ways that you could use to get started with payments so for the entire month of September we&#39;re gonna have like different Advocates companies we need to have some Engineers some PM folks um CJ is going to be there I&#39;m going to be there we&#39;re going to look at some Ruby stuff some.net stuff right we&#39;re going to spend the entire month talking about checkout so hopefully y&#39;all join us um next month and uh again if you&#39;re just getting started with strip I think is a great place for us to start um the next thing I want to highlight for you folks if you head over to dev.2 a lot of our team you know write blogs articles and stuff like that over at dev.2 our teammate Paul has uh interesting post call purchase fulfillment with checkout or you know wait what was I what was it that I paid for so pretty much what he&#39;s talking about is after you&#39;ve collected money right like after you&#39;ve collected uh your payment through stripe what do you do right like what&#39;s the process after that and he kind of walks through you know you know after you&#39;ve gotten your like successful paid event like you know how can I get like the line items you know I mean how can I kick off some background process like what&#39;s some of the the the the recommended ways for us to kind of handle some of these things um using stripe web hooks so uh again this is over on dev.2 um under the stripe organization I think they call them organizations in dev.2 is that what they&#39;re called CJ or groups or whatever I think so yeah I just dropped a link too so you should see that in the chat uh if you want to head over and take a look at that article one of the biggest gotchas with checkout is when you receive the checkout session completed web hook notification the event payload does not include the line item so you have to turn around and re-retrieve the checkout session and expand those line items this is like one of the most common questions we hear it&#39;s designed like this so that we can make that API really perform it for everyone and so if you&#39;re wondering like wait a second like how do I get the product or the price that was purchased with checkout this is the article for you for sure yeah so definitely go ahead and head over to dev.2 under our stripe organization and you can learn about that over there also super quick so you know we love Advocates from like all kinds of other companies too so I want to highlight some of the other things um some folks were working on our friends over at OCTA slasher are doing um a Dev day so this essentially is like a little mini devrel tour it looks like they&#39;re growing all over the place they&#39;re going to Seattle and Sydney and London and Berlin um probably some more countries that might pop in there too I don&#39;t know maybe we&#39;ll see what happens but essentially they&#39;re doing like Hands-On workshops and meet and greets and and really just giving folks the ability to like be in person and work with the team and kind of learn about some of the the different things that are happening within this space of authentication because as you can imagine they&#39;re they&#39;re off company and they do those types of things so if you&#39;re interested or if you know you&#39;re in one of these cities or maybe you want to go to one of these cities for vacation um definitely go ahead and check this out I think this could be a really interesting thing because you know I can&#39;t imagine a website or application that does not need off I mean you might need less often than some people do but like I think we pretty much all need like some level of security for stuff so definitely go ahead and check out our Dev day and the last thing I want to talk about what I&#39;m most excited about I&#39;m not gonna lie about it I&#39;m not gonna hide my excitement uh the Caribbean developers conference is happening uh November 3rd through 5th um it&#39;s going to be in Punta Cana the Dominican Republic we have a few Stripes that are growing uh myself I&#39;m going and also my teammates uh Mike uh is also going as well so you know we&#39;re going to be doing some workshops and some talks about stripe and also we&#39;re going to have some little behind the scenes things that are happening like you know little uh thought leadership sessions and stuff like that that we&#39;re going to work on um really just trying to you know reach out and kind of show folks like really what&#39;s possible and on top of that too I think this is a really great lineup of speakers there&#39;s a lot of amazing folks that are coming a lot of representation from tons of different companies and so hopefully you all will join us and uh you know we&#39;ll have a good time down at the Dominican Republic now that being said this is the part where I say this is no longer an essential show and now this is all about Chris so why don&#39;t we start talking about engines so engines um I know what gems are I know what plugins are at least I think I know what plugins are I&#39;m assuming plugins are like universally generic right throughout whatever programming language you are but I kind of feel like engines are something different like are they different are they the same thing are they like some hierarchical like hierarchy of like sure relationship like like what are they like how do they work yeah yeah um a ruby gem just for anybody that&#39;s not familiar like is just a ruby library of code that you can access and use and take advantage of um and then a rails engine is specific to rails and gives your rails app features and it can do stuff um automatically because it knows that it&#39;s a rails app so you might write a ruby gem that can do you know time calculations or something but it may not have any idea about where you&#39;re using it or it doesn&#39;t need to but if you want to do something like pay where we want to provide um database models and uh you know webhook processing and background jobs and things like that then it helps to have something like a rails engine so that we can integrate deeply into your application and take advantage of all the features of rails that that uh we know we&#39;re there and exists and you know don&#39;t have to be inside of your code so that&#39;s kind of the difference between like it is a rails engine is a ruby gem but it knows all this context about rails and what rails can do for you so we can really integrate out of the box and and have everything ready to go without wiring up things manually for you does that make sense okay yeah that makes sense when I think about a gem then I&#39;m thinking about I don&#39;t know a library that does a specific thing like hey I need I don&#39;t know a QR code thing or a password and then I&#39;m going to call into that function to do some work for me versus an engine if I&#39;m not mistaken is like an add-on right that just does some extra things and I just have to add it on and then that functionality is already essentially like wired up and I don&#39;t have to be as involved in the process from a developer perspective yep yep yep so like a good example of that is the web hook routes in pay when you install the pagem uh will automatically add the routes for you to your rails app so you don&#39;t have to do anything you just get these pay web hooks stripe and voila you&#39;re good to go so there&#39;s no setup for that it just is automatic you could turn it off or customize it of course but um it knows you&#39;ve got a rails app so we can add those routes in and be you know Off to the Races with no no code written yourself which is great got it okay well yeah well well how do you how do we want to do this are we gonna are we gonna write a gem from scratch or like a engine from scratch or do you have an example that we could take a look at and kind of walk yeah we we could um so I uh was gonna pull up the rails guides real quick and and show you know this is the place to go if you want to like read more in depth about them and and all of that stuff okay um there&#39;s a few different options that you can do uh such as a mountable one um or a full rails engine and there&#39;s also another thing I should mention there&#39;s what&#39;s called a rail tie as well which is like a smaller engine so the rail tie will integrate with rails but it won&#39;t provide like the in a way a rails engine is like a miniature rails app that you can put in any other rails app and the rail tie is kind of the you can build a plug-in to rails without the um the app folder so no routes no control well you could probably do routes if you want but um no like controllers and models and things so it&#39;s kind of a lighter weight version of that um so yeah I would recommend you know check out the guides on here for always getting the latest ones but it&#39;s going to work very similar to a regular um rails uh engine or a rails application so let me actually pull up a different window here real quick and another thing that I&#39;m thinking if I already know how to build a rails app then I already know how to build an engine for the most part pretty much pretty much yeah there are a lot of little things that you will um you know learn as you go but there is um we&#39;ll just copy this example but we&#39;ll see like all of the we&#39;ll do a full version of this what we&#39;ll see is like a lot of standard stuff that you would in a normal rails app so oops let&#39;s go into Lord and pull that up but you&#39;ll see a lot of stuff that&#39;s pretty standard you&#39;ve got your app folder with inside of it assets controllers helpers jobs mailers models and Views just like you would with a regular rails app so it&#39;s a nice way to kind of blend your rails app with some reusable code that you want to put in multiple apps like the page M we want payments and a bunch of rails apps so we can just drop it in and all of this stuff can like live side by side but it&#39;s all hidden away inside the library or the rails engine so that&#39;s pretty awesome um and the way that it works is you&#39;ve got a ruby gem so your ruby gem has a definition of a set of files that it is going to include and the default generated here is everything in the app directory config DB and lib and all the files underneath them um and it will automatically load the file with the name of your gem so our module blorg here will be loaded and it will load this file and it will load the version and then the engine which is the rails engine so this is an empty file that just says hey we&#39;re gonna Define a rails engine and then rails knows how to keep track of all of those when they&#39;re loaded and fire off any of the callbacks so there&#39;s a lot of times where you might build something where for example in Pay we have a Pay customer method and actually let&#39;s dig into that real quick I&#39;ll show you that in Pay itself when we go to the pay engine um we have these initializers and and other callbacks that we can set up so for example when the paint engine loads we can initialize our payment processors and we can set up the routes automatically and say hey uh we&#39;re going to mount the pay engine routes to a certain location and that&#39;s pay slash pay by default that will add slash pay slash web hook slash stripe and set everything up for us but we can also do some other things like when active record loads we can include a module to add features to active record database models automatically so this is just a little thing that says hey we&#39;re going to sit around and wait for that to load and rails has a specific order of loading your rails application and the engines and then um you know it will go and load certain files and folders in a specific order so this is going to make sure that if we ever reloaded our application and development it would also reload and make sure the pay attributes are in there too and that&#39;s basically how we add the if we go into that file I don&#39;t know it&#39;s going to jump to it for us but that is here under attributes that is just a concern that we include in there and and gives you the um the there it is the Pay customer method once you drop into your user model or your account model or whatever it is and those can say hey we&#39;re going to include other things we&#39;re going to set some variables and whatever else we might want to do but that&#39;s one of the ways you can use an engine to hook into different parts of the Rails loading process which is cool so quick question then for you so if if an engine is just like an additional Ruby app I&#39;m sorry a rails app technically like is there any concern around performance when it comes to me I don&#39;t know let&#39;s say I added like five engines to my app or yeah like like like what are the limitations what are things that can be should be concerned about from a performance perspective as I&#39;m like adding these things to my app or even developing my own yeah um rails in general is pretty good about that because of uh the autoloader and now site Works amazing as the default autoloader so all of your typical controllers or models and any of that will be loaded whenever it&#39;s referenced so um it not it doesn&#39;t actually get loaded immediately um which is nice so performance isn&#39;t really something you have to worry about too much unless you are riding a lot of requires and doing things manually in your code um you might actually load all these files and it would slow down booting up rails uh pretty bad so all of these kind of stick to using the rails uh conventions and having those things Auto loaded for you will basically make it all work uh like your rails app normally would which is nice so you wouldn&#39;t really run into any performance things like that unless you were kind of you know loading lots of stuff individually so it&#39;s nice like when these uh for example that engine include that we had here so the whenever active record is loaded we include this this is going to just say hey run this whenever don&#39;t we&#39;ll set it up to run later on and we don&#39;t ever really know when activerecord gets loaded so it&#39;s lazily executed and just cues it up to be ready whenever rails or your application loads active record um it&#39;s it&#39;s lazily executed so it&#39;s not going to run the code right away which is good so helps with boot time and things like that okay so super quick question coming in from Pierre in YouTube and this is somewhat related to what we&#39;re talking about right now and that is so an engine is sort of a microservice outside of our app um and I&#39;m I guess the answer is no but I&#39;ll let you answer that real quick yeah you can think of it as a micro service in a way but it&#39;s going to live and run just like every it&#39;s as if this code was in your rails app like everything else you would have written yourself um so it&#39;s really not a separate service it runs all together with your rails app all the routes the controllers everything are treated the same um so it&#39;s not running separately so it&#39;s not really a micro service but it&#39;s a way to put it in a container and you know make it a separate thing that you can think about and reason about um as its own module that you can take and reuse in different places and things like that so you can treat it like that where you&#39;re thinking about it separately but it&#39;s really not a separate you know service or anything okay and then I think my follow-up questions that would be so you just showed a little bit how you know you could kind of plug into like the the boot up sequence there a little bit is it a case that as as my as I&#39;m building my rails engine I&#39;m guessing like there&#39;s different life cycle Hooks and events and other things that I could kind of tap into that&#39;s a part of my main application and now the the the engine can just be like okay I want to run at when this thing happens or when that thing happens or at this particular I don&#39;t know event or something like that yeah yeah and a perfect example of that is uh this block right here where um when you are in development rails will periodically reload files when they get changed um so you don&#39;t have to reboot your application for changes and this to prepare block will get called when those things change so this um if we reloaded the pay stripe module and it lost our API keys or whatever this would get re-called every time that it&#39;s reloaded and it would make sure that everything is set up correctly and that&#39;s kind of the same thing here we&#39;re just setting a call back to say hey anytime you reload activerecord make sure that the pay attributes are in there there&#39;s a common um issue that a lot of people will do the first time around is you will when the rails engine boots you&#39;ll include this module in active record just the first time but when it reloads it will clear everything out and reload it and you need this to happen the second time and third time and fourth time because if you don&#39;t do that your code will work for a few minutes you will save something it will reload and then it&#39;s broken and so you need to make sure that you hook into the life cycle event like that in order to make sure that you know your extensions are actually going to be there permanently the initializers are ones that are just something that happens when it boots up so it runs one time and you&#39;re good to go for example we don&#39;t want to add routes every single time the rails app reloads because we would end up with duplicates so we just do them once here instead of you know on a life cycle kind of callback and there are a lot of various different things that you can do I know that the notice gem that I built uses a similar thing but it uses a um where was that there is somewhere in here that it will actually like extend the eager load paths um so that or that was in Mad Men I bet um it will actually add New Paths to look in the folders for different files so here we run before your rails app is fully configured We&#39;ll add some files and folders to the load path to look for auto loading files for you so that&#39;s an example of another callback that you might want to uh to hook into for different things okay that makes sense so if I know Ruby I could write an engine and like you say I can plug into these different event Hooks and now I could just you know I could extend to like my heart&#39;s consent I&#39;m I&#39;m curious now about like in your experience because you know like you said Pay is pays pays like uses or is an engine right or or something like that and you&#39;ve been developing it for a while what are some of the things that you&#39;ve seen that you&#39;re like okay this is important for people that are Building engines to know about so that I know you don&#39;t you know run into a lot of problems later down the road yeah um I think the biggest one for me has been uh the database migrations because originally pay was designed where um you had a model and you would include pay onto it and it might be your user and you want to have the user pay for things we would have you go add fields to your user model and that was fine for a while but as we needed to change those things it became a really hard maintenance thing for us to change because you&#39;ve written migrations uh that have added things to your models we don&#39;t know which models they are so we have to keep track of them somehow so there was some code that was like monitoring for that stuff and um it just is really tricky for you to go and apply your code to models database models that you don&#39;t control so one of the examples there that was bad was like if we need to add new feature like another field you had to as a user upgrade pay and then go run a migration yourself and there&#39;s really no step that tells you hey this new version needs this change unless you&#39;re reading the change log and that&#39;s not something that people always do so they&#39;ll learn it the hard way when things break when they upgrade the version and then add you know issues asking like why did this break and you have to explain it and it&#39;s just like a painful process there to maintain that so you don&#39;t want to do that and then the other thing is if you&#39;re using these models that you don&#39;t know about um you have to figure out how to keep track of them somehow so for pay for a while I had set up a thing where any class that you would use that included pay we keep track of that every time and then when a web hook would come in we would say uh you know a subscription was created for somebody and we&#39;d have to query the users table the accounts table the teams table whatever models you had and it could be 15 if you wanted so we would have to do this like multiple database queries trying to find the correct um record and that wasn&#39;t great either and I realized that rails has a good pattern for this and they do this in several of their own rail ties so when um when you go to well let&#39;s go to rubygems.org rails gems rails yeah so rails itself is dependent on a bunch of engines itself so action cable and action mailbox and so on are all rails engines and if we look at like action text um and we go to we can go to GitHub and see that rails rails and we go to action text it&#39;s going to have an engine file in here as well so even the core rails features themselves are um our rails engines which is pretty neat um but this one is one that has database models in it so inside of app we have models action text and we have these three different models so it&#39;s great because if you are riding an engine you can create your own models and control everything about them so as a user of action text I know that these database tables and Records all exist but it really discourages me from modifying them because they&#39;re kind of Hidden Away inside the gem which is good so the maintainers of the gem can make their updates to it and trust that you know it&#39;s not going to be heavily modified by the users of your rails engine so that&#39;s beneficial for uh upgrades in the future because you can add migrations the users still have to add those migrations to their application as you update your versions but it&#39;s much easier because they don&#39;t have to touch any code and modify that because your new version ships with all the code the only thing they have to do is change the the migrations so that was probably the biggest like pain point of working on pay and trying to get that um in a more easily maintained State because it&#39;s it&#39;s troubling to uh try to maintain that and have users modify their database in sync with your changes and it&#39;s much easier to kind of control it all inside your your engine itself plus um you can just have associations instead so the way that action text works is you might have a blog post model it has a relationship to an action text Rich text and that would just be an association to another table you can delete that table and you know modify it and it changes functionality inside your rails engine without affecting the um the blog post and that is really nice because you have a single place to interact with all those as well so for pay we now have a Pay customer table and instead of storing that on your user model or your account or whatever we now have it inside our own table and when a web hook comes in in we can query a single table now instead of coring n number of models that you might have defined so it really makes it a lot more consistent for you as the developer of the Rails engine to like work on your own code as opposed to trying trying to blend the user&#39;s code with yours so it&#39;s it&#39;s um probably the biggest you know most important thing to pay attention to when you&#39;re trying to build something that integrates um tightly to a rails application that makes sense yeah that makes sense um looks like we have a quick question coming in from YouTube I&#39;m going to try and read this out real quick uh it says adding migrations through engine updates would actually update the schema and actually update the database on just updating the version of engine trying to understand what that question exactly um well I guess it probably um so in general like the same question so like or I think it&#39;s the same question it&#39;s like when you release pay version four like you already had paid version three and pay version three had certain migrations and when you release pay version 4 do you release a new migration that will add new columns or change the database yes and that&#39;s that is what you would do yes um so here&#39;s a good example active storage originally shipped without certain columns um and I forget it&#39;s like the service column or something like that service name um and what they&#39;ve done is separated out the database migrations so if you&#39;re installing active storage for the first time you get the regular migration which includes everything that is up to date but if you have a previous old version of rails and the old migration it will give you these migrations to update you to that latest version and what it should be so this one adds the service name as it says in the name add service name to active storage blobs so it will go ahead and check and make sure that you have the active storage blobs table it will check and see if that service name column exists because you might have added it yourself and it will go ahead and make sure that all of that is correct and what&#39;s cool is the rails engines have a little helper for this so when you generate your gem your rails engine it comes with a rake task that will be called your gem name install migrations and that&#39;s going to look inside the DB migrate folder and then it will copy those over for your users so you can basically ship new migrations and then your users just need to run this command a second time or a third time or whatever whenever they do a major update it should copy over the migrations that they need and that will basically make that similar to how you would just run your own migrations which is nice okay so another thing I&#39;m thinking about as we&#39;re kind of going through this is assuming I can have more than one engine which we can&#39;t already do because you did mention that like rails itself is like a composition of additional engines assuming that I can have multiple engines should I be concerned about like conflicts when I say conflicts I can imagine what if my engine is is reliant on some other gem right and your engine is reliant on the same gem but a different version of that gem right like I think that could be like I don&#39;t know maybe it is like one way to consolidate and also what if my engine again I&#39;m just in the realm of conflicts what if my gym you know I don&#39;t know rights to a certain table web hooks very generic name web hooks right and then your gym has a web hooks table and so now we&#39;re both writing to a table called Web hooks right I mean is there some type of namespacing or scoping that can happen that says everything at least from a data perspective and even from a routing perspective for this gem lives in this space or do you have to like be very specific with naming conventions and things like that to make that happen so yeah two things one one is um you you will in your gem spec um already set version requirements so if you have two gems that require different versions of some dependency that&#39;s shared on both of them you&#39;ll want to make sure that that&#39;s in your gem specs so that when you install them it will say Hey you need compatible versions of these two um engines to make that work so that&#39;s one thing if you have dependencies that are you know shared between them a common example of that is the oauth libraries you might have oauth with GitHub and Twitter and Facebook and whatever um those will all depend on different Omni auth dependencies and if those conflict then you have to you know Fork them and resolve them or whatever the case is and then when it comes to code stuff and data things what you&#39;ll see here is that it this migration for active storage creates an active storage blobs table and if we go to the model for it the models are actually all namespaced inside of active storage so app models active storage folder and then we have blob um so the the models are going to end up being namespaced accordingly it also makes sure that the table name is namespaced in your database so if you have any of the pay uh models in your application what you will have is pay customers instead of just a customers table which was probably going to conflict with somebody&#39;s application or merchants or payment methods or whatever everything is namespaced so as long as nobody else is using that pay namespace it&#39;s all going to be safe that is the main thing you just need a unique name and namespace for your your engine to keep everything inside of and that is like the nor normal thing for any ruby gem anyways so you will have when you create your ruby gem it will give you a module to work inside of and we can see that here too we have our module blorg in the brand new empty rails engine that we created so inside of that blorg engine is going to be namespaced engine will be used in multiple gems so we wouldn&#39;t want that to be like a top level thing so it&#39;s nicely organized for you and that&#39;s really all you have to do is just make sure that your tables and your classes and everything stay within that namespace and you&#39;re pretty much good to go so okay that makes sense when it when it comes to the generating views from the engine is that like I know with devise right you can say like generate all the views for me so I can go and edit those yes that&#39;s built into like the engine system or do you have to build that it is okay it&#39;s super cool so so if you have an engine so a rail tie would be basically this without the app folder but if you have an engine it will automatically include the app folder when it&#39;s searching for views so your rails app is going to first look at your app folder and app views device you know sessions new um so your rails app can override those easily because it&#39;s like first in the path like the search path so rails keeps it track of these search paths automatically because you said hey we have a blorg engine here or a pay engine we&#39;re going to include that in the list of search paths for the views and controllers and everything else so you can go ahead and drop them in to your rails application to override the things from the gem so it&#39;s just kind of seamless for you which is really handy because you can just you know modify stuff really easily and override it however you need if you need to change the design copy the file voila you&#39;re good to go and that same thing applies to um generators as well and I think we may have a generator here so rails Gems or engines and rail ties will have generators so we have the emails views generator and this will say that when you run the like rails uh pay you know views email views generator it will go and look for this directory and it&#39;ll copy over all of the files in there to your rails application so it&#39;ll grab the stuff from the gem and you know copy it into your rails app and that&#39;s really all these generators do is copy the files straight from inside the gem and put them in your rails app so that&#39;s how it overrides it just copies them from one place to the other and you&#39;re good to go that&#39;s why these directory values here are exactly the same because they&#39;re they&#39;re in the same spot so you but you had you did have to like make that generator it&#39;s right this is yeah so this one you like run rails G um and you&#39;d need to do this in actual rails application but it would print out all of the like generators that are available right one of the things that a rails engine a rail tie will do is inside of your library it&#39;s going to look for a generators folder and you can put generators inside of that so um all of these will automatically be detected and registered and then be part of your rails command so when you run rails generator or rails generate it&#39;s going to look at your rails app pick out itself and all the engines look in the those folders then look for the lib generators folder and you can use that to like create your own generators or in the case of something like rails J Builder that one overrides the rail scaffolds to include Json in them and this one has the scaffold controller generator that overrides the rails scaffold controller generator to include Json in the uh in the controller itself in the in the json.j Builder views so you can build these to override the rails generators themselves as well if you if you wanted to do that so you could theoretically inside of pay have a controller for pricing and then you could say like okay here&#39;s a pricing table and if you exactly edit that yourself you would just say like rails G pay views and that would copy all the views over you would go in update it okay yeah and we would probably end up doing like a pricing generator itself or something that you would give us maybe the ID of your pricing table we could insert that into the HTML and then copy that over to your rails app and you&#39;d be good to go or whatever so yeah lots of lots of interesting um things you could do with that to basically create those files automatically and you know do some magic to uh generate a pricing page in like one command something that I&#39;ve always found challenging is like when I generate the views for something like devise it doesn&#39;t have whatever UI framework I&#39;m using so it won&#39;t have bootstrap or it won&#39;t have Tailwind or it won&#39;t have whatever and so I always like I&#39;m always super annoyed that I have to start from scratch basically once I copy things over um so yeah like what yeah how would you approach kind of building something that fits nicely every time you want to use views but create separate every single framework and you won&#39;t be able to you won&#39;t be able to tell it how to get Tailwind or bootstrap or whatever CSS framework because it could come from the asset pipeline it could come from es build or webpacker or whatever you might be using for your front end so your HTML you can easily drop in but you would kind of have to say hey we assume you&#39;ve got bootstrap already here we&#39;re just gonna like have the HTML with all the bootstrap classes on it and that would work fine and if you have any JavaScript that is needed you might need to embed that or you know have that some other other way one of these being the Tailwind CSS rails library that dhh I guess just updated which is cool um it has a generator and it will override the scaffolds and overrides like the Forum here with the um all you know all of the CSS and stuff for tailwind and your index page will have like a table or whatever flex stuff like this so if you did that you would pretty much need to create like several different folders probably uh maybe different generator commands or maybe the command has an option and you would pass in like I want bootstrap or Tailwind or whatever and then it could your generator could decide okay they said bootstrap so we&#39;ll go into the templates folder in the bootstrap folder and then we&#39;ll have our copy of files there that we move over um because I don&#39;t think you&#39;re going to want to put a bunch of if statements inside your HTML templates and try to like organize that because a lot of times your Tailwind or your bootstrap is going to have different HTML layouts anyways so you couldn&#39;t really make one template that supported both really totally what&#39;s up if that makes sense yeah yeah um one thing that I&#39;d love to see is any gymnastics that you&#39;ve done particularly around database queries inside of pay to paper over all the different database Management systems that I know yes um yeah and that&#39;s one of the tough things so like pay is uh trying to support you know sqlite MySQL postgres and I don&#39;t we also support multiple payment processors so they&#39;re not all the same and we don&#39;t really want to create uh you know all these different tables that may be used sometimes for one or the other so we try to consolidate them one of the easiest ways is to try to consolidate them using a Json or Json V column um so I know that we have a lib file here and pay adapter and this one allows us to check your database connection config and see if you&#39;re using postgres or not we try to use the Json B column there and if you&#39;re on sqlite or MySQL then we&#39;ll use a Json column um and then this just kind of helps us run the migrations and say which column do we want for that type and then from there we have to and I know Colin just worked on this with me for querying those tables they&#39;re all very different so I think if we go into um yes here we go so inside this we added this code right here to query the Json columns uh between the different database versions so postgres and postgres uh use the Double Arrow and this works to query those Json columns my SQL has a double arrow but it doesn&#39;t work unless you have the dollar sign dot before the the name so we were hoping that because they have the same operator we could just have them all treated the same of course you can&#39;t this will just return nothing um and then sqlite just introduce the arrow syntax as well and we&#39;re super excited about that and we could have Consolidated maybe that MySQL 2 and sqlite together but it turns out that for backwards compatibility the brand new Ubuntu version that came out in April um doesn&#39;t have it&#39;s one one minor version behind for supporting that syntax so we have have to use the Json extract instead and the basically this Arrow operator is a shortcut for Json extract and you&#39;ll see it also requires the dollar sign Dot at the beginning of your column name there or your attribute in Json so we have to do some of these uh you know jumping through hoops that are on fire in order to like you know make the stuff compatible unfortunately uh the mariahdb stuff which is like a fork of my sequel uh or whatever they claim to be like fully MySQL compatible but their Json columns are actually text columns that are validated to be valid Json but they don&#39;t actually have the same operators and so we&#39;ve tried in the past to uh do the same approach here and support that but it just didn&#39;t work so maybe in the event in the future they&#39;ll fix that but they like used it as a text column in order for some performance reasons uh to make it faster but apparently now you can&#39;t query it the same way so it it is not compatible and I wasted you you know hours trying to figure out how to do an equivalent of that as well and so yeah you get in the weeds real fast when you&#39;re trying to support multiple things like this seamlessly and there&#39;s plenty of users using all three of these databases so uh that I guess brings up one real quick thing uh which is when we run our CI we have a whole heck of a lot of different uh Matrix of things where we need to test each database with each version of Ruby that we want to support with each version of rails so that means that for SQL light we need to run it against uh four different versions of rails and a single Ruby version and that means that we&#39;ve got to go modify all those and we end up running like 12 tests for sqlite or 12 iterations of CI uh for that in postgres and MySQL so it uh it keeps the CI busy um because we have so many different permutations of those and it will probably only get worse but luckily like we can drop uh Ruby 2 6 or whatever rails five two whenever it goes end of life uh and just only officially support the latest versions so so it seems like that like doing those gymnastics around querying if the pause behavior is null is a choice that you&#39;re making as an engine maintainer because it would be easier to just use this Json blob for all the data related to a subscription rather than introducing this new column that like would force everyone to run a migration and maybe you have to like figure out how to backfill etc etc okay yep because um some payment processes processors don&#39;t even support pausing at all so uh We&#39;ve leaned on things that are not very often queried we&#39;ll put them in the Json column in this case maybe in the future we will add a migration that will move this to a you know pause Behavior column or something like that but not everybody sometimes it&#39;s just like pause is true or false stripe has multiple options for that so we have to make sure that like we don&#39;t go too overboard on tying it to one specific implementation because we&#39;re trying to abstract this stuff so this has been um our solution for now because this I think is maybe one of the only things that we actually have to query in the Json columns um and this is mostly just to keep a we didn&#39;t this is mostly for convenience because in reality all of the pause subscriptions are technically active so we could load all those and in general I want to display them all on the the web UI but maybe for like authorization of does this user have access to the paid feature active without pause is a helpful um query to make so that we can say hey these are all the people who actually have uh access to that feature because if you&#39;re paused we don&#39;t want to give you access to the paid features um so it is one that you know probably could make sense to uh actually pull out into a separate column or something in the future but it&#39;s always a trade-off of like we&#39;ll end up running 100 different migrations if we&#39;re going to try to like sync every one of those different keys that stripe may or may not change in the future so the nice part is with the Json column we add the attribute and we&#39;re done and you upgrade the gem and you didn&#39;t even know that we added new new fields and one example of that is like all the stripe tack stuff we now send call the line items we need discounts the tax uh amounts and all of that stuff just get dumped into the charge model and you&#39;re good to go and generally you&#39;re not going to be querying on that so it&#39;s all pretty solid uh just to to jump in there so here&#39;s a good example of lots of the different things that we store in the Json column and we can easily rename those in the future and whatever else add add new ones drop ones and it doesn&#39;t really affect the usage which is nice awesome quick question I&#39;m sorry yeah something you want to say CJ no that was it I was just yeah this is uh I&#39;m learning a ton so that&#39;s good hopefully everyone that&#39;s watching is learning a sun too if folks that are still here with us if you have any particular Ruby uh any rails engines that you really like you think are really cool go ahead and drop them in the chat and we&#39;ll you know we&#39;ll pop it pop it up a little screen and we can we can take note of those um so we are running a little bit late on time we have about well like five ten more minutes uh before we gotta you know get back to the real world um question I had for you Chris is there is there a use case where my engine needs to like talk to or like glean insights about how my main application is running I know we spoke about like CSS stuff and assets and stuff like that but like other than that like is there like I don&#39;t know like anything that it needs to like functionally know like can it call into my app and be like hey I don&#39;t know I want to ask you a question or get like some information or you know figure out like the state of configuration or whatever it is like is is that like a thing that people do yeah absolutely um a good example is actually in the uh the madman repo we have a generator that will generate so this is a little admin um gem that I had worked on that looks at all of your database models and then creates an admin interface for them so in our generator we have it uh in the install generator I believe it will look for all of the models in your rails app so we&#39;ll go find everything that has inherited from active record base and it will check to see as long as it&#39;s a real um a real database record not an abstract one our database table and the has and belongs to many in rails are kind of invisible so you don&#39;t actually have any code to interact with those database tables um we skip those and look for any models that uh match that and that&#39;s it so we can look into that stuff from the rails engine as well and you can also like do I think it&#39;s probably here in in pay if we go into the engine you&#39;ll notice that in the routing piece um we in our initializers are given the rails app that we&#39;re integrating with so we can actually go and interact with anything on that so in this case I&#39;m saying hey the page m is loading you told me to Auto Mount the routes so we&#39;re going to tell the rails app hey we want to append this route and it is going to be all of the stuff inside of it so you have access to that you can look up any configuration things there&#39;s lots of cool stuff that you can do with that like the uh I don&#39;t know if it&#39;s under brails itself there it is um sat rails is a good example of this where it will go and it&#39;s a rail tie um well it might be under the sassy rails gem instead let&#39;s pull that up sass C rails sassy rails um it will actually go and configure things inside of the Rails application itself and like change configuration values so it your engines can actually Define their own config that&#39;s separate from or it&#39;s it becomes part of the Rails application config and it can also tell for example that the app generators should use these SAS templates by default so it can tell your NJ Builder does the same thing like hey we want to make sure your rails app when you run a scaffold it includes for this uh SAS or scss files jbuilder will say hey let&#39;s make sure that when you run the scaffold we&#39;ll include the jbuilder stuff you can do all kinds of Integrations with the rails configuration in the app itself and so they really provide you like whatever functionality you could want to dig into the to customizing the rails app itself so it&#39;s pretty cool got it that makes sense cool um I&#39;m trying to think if I have anything else to ask you also my mind is like partially melted because I&#39;ve just like it&#39;s absorbing so much information well there&#39;s a lot to it Chris said he promised us a teaser uh so we did so I&#39;m kind of curious about how that&#39;s going and also yeah see I&#39;m I&#39;m also selfishly interested in how your experience was integrating with metered billing uh yeah um so yeah speaking of all that the well you guys released version seven of I need to make a new release uh entry here in um in GitHub but I released version five made a typo and then released 5.0.1 um to update pay to the latest stripe version 7 of the Ruby Library so that&#39;s been um exciting but recently we like uh included all of the stripe metered billing strike tax and things like that in order for Jumpstart Pro customers to have all that functionality like natively built in your app we&#39;re all white labeled so we&#39;re not redirecting you to checkouts it&#39;s like a nice themed experience and one of the first use cases of that is going to be the new the new hashbox so we&#39;ll have um metered billing I&#39;ve got my own account on a free plan here but you can go through the checkout and we&#39;ll have the uh servers that you sign up with and everything will be kept track of and we&#39;ll I basically written and I&#39;ll write some box in the pay docs about how to do this but for every server that you spin up and shut down we basically will just keep track of the last time we recorded usage and we can set up a Cron job or whatever to run every hour every day every week however often we want to check in see how long your server has been running give the stripe subscription that update for the usage record and then stripe takes care of the rest for the metered billing stuff so it&#39;s pretty awesome um was that challenging to integrate into pay or like are you is there like a new usage record thing that&#39;s part of pay or so all we did which I&#39;m pulling up right here all we did is uh we have a create usage record method and you just give it the um quantity in the action and it&#39;s good to go we will check to see if we can if you have a subscription item id given to us we&#39;ll use that but we&#39;ll just assume it&#39;s the first one if not and that&#39;s it so in our case like if you wanted to do a um you know purely metered billing this is like the simplest thing you could do if you wanted to have like a base fee plus metered usage then you would have to specify the subscription Item ID on there in order to to do that um and you would just probably save that in your you know subscription or something just add that in there and without having to query for it every time but yeah yeah that&#39;s what I that&#39;s why I did something similar on the subscription item that you get back from stripe the usage type or the license type one of them will say metered and one of them will say licensed and then what I was doing was like find the subscription item where it&#39;s metered and store off that subscription Item ID and like let&#39;s use that one so I don&#39;t have to worry about trying to like create a usage record for a non-meter yeah and and if anybody wants to do a pull request uh I think it would be a great Improvement to have this check for rather than naively just grabbing the first subscription item go find the first metered subscription item in there it should be available because I think when we sync a subscription item uh where is that subscription items somewhere in here oh here it is yeah we yep there it is right there so we set it to let&#39;s see attributes metered it&#39;s true but subscription items we&#39;re not grabbing the usage type here so it might be nice to also save the usage type in here so we have that rolling and grabbing the Ida Price metadata and quantity so that would be great to add usage type in here and then we would be all set to be able to update that down below so yeah I saw your your screencast on that and I thought that was a great you know solution for it so that it&#39;s like here we have the subscription ID and the item that we care about um because your monthly flat fee you don&#39;t you don&#39;t need that ever but for this endpoint you do for the metered usage so cool yeah yeah we&#39;ll have to go and update this so that it&#39;s even even a little bit more robust which would be great so super yeah very very cool I think yeah just metered meter billing in general feels like a more advanced way to Bill people but also it aligns the value to your cost center so as a business like oftentimes like in your case for hatchbox right like your cost center is like number of servers or whatever and so being able to Bill based on the number of servers makes way more sense and so I do think like going forward that&#39;ll be a more and more common thing that folks want to build so the fact that it&#39;s already available in Pays phenomenal because yeah people can go just create YouTube yeah and that&#39;s that&#39;s the cool part about working on on a product outside of pay as well it&#39;s like uh if I need to collect tax then well I&#39;m gonna go build it into pay then it&#39;s going to be a free Improvement in jumpstart for any customers there and then I&#39;m using it myself so I work through all the bugs and all whatever else and you know have a real use case for it and I can go back and include docs or whatever and it was like earlier today I was telling Colin like I wanted a free trial um that you know we didn&#39;t need to create a customer in stripe or anything but I know we can do that where we can create a subscription without a card without a payment method now which is awesome um but I had set this up and we just had a little fake uh subscription inside of the page M for users whenever they create a new account we just create a a little fake subscription for uh seven or 14 days and then when that&#39;s over we&#39;ll have them sent over to stripe and we can create the the stripe customer and everything there but we could also do it the other way too and just have it create the stripe subscription right away and ask for the payment method later and fill all that out which is awesome so lots of different little ways to to tackle that but metered billing I think is yeah a great option because you are really tied together there the only like tricky thing is if you&#39;re paying first four stuff and the user doesn&#39;t uh maybe their card doesn&#39;t work when you finally charge them then you might be out that money or whatever so that maybe is the one thing just to keep in mind if you go that approach but in our case like on hatchbox like if we lost a month of usage it doesn&#39;t cost us anything because we&#39;re actually deploying to servers you&#39;re paying for instead of like us paying for servers and then we would lose money if you uh you know didn&#39;t pay us at the end so we&#39;re nicely positioned for that which I think is good definitely a risk for sure yeah you know but I think if you get it to work well that it&#39;s just such a nice thing that you&#39;re not paying for you know unused things all the time and I think that is a pretty common situation with tiered pricing you&#39;re just like well we have one extra you know email subscriber and now I get bumped up to this like several hundred dollar more tier and just because of one person and it just doesn&#39;t seem like it makes sense you know totally so yeah well folks I think we&#39;re on time um Chris thank you again because every time you come on I feel like we learn a lot of cool and interesting stuff so I definitely appreciate you yes yeah thanks for having me yeah and then thank you for everyone that&#39;s here and that&#39;s been like dropping comments and you know giving shout outs and I feel like a lot of folks in the chat their minds have also been blown so you might need to give them a minute to catch up before you know we we uh bring them any more Dev chats but um again thank you all for watching and thank you for being here we&#39;ll be back think in two weeks is it two weeks next week what am I doing will we not next week uh Wednesday we&#39;re gonna have some uh cool stuff about stripe checkout and you know again for the whole month of September too so please come back please hit the Subscribe button hit the like button if you&#39;d like first to have Chris back on and talk about some real stuff in the far future because I&#39;m sure you had some some busy things that are happening soon um let us know and uh we could uh you know we can get that sorted out all right thank you all so much sounds good and we&#39;ll see you again the next time we have Dev chance bye folks next time Chris thank you [Music]

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