---
title: Rails scaffold deepdive
slug: rails-scaffold-deepdive
published_at: 2021-08-09 14:00:31 +0000
updated_at: 2026-03-04 20:14:01 +0000
summary: 
description: Learn all about what you get when generating a scaffold with Ruby on Rails. This covers many Rails conventions that follow the happy path and are often sensible defaults. #rails #rubyonrails
tags: [cjav_dev, web development tutorials, web development for beginners, vim, ruby, rails, javascript, rails scaffold, ruby on rails tutorial, rails generate scaffold, rails generate, rails g scaffold, routes, params]
views: 5424
author: CJ Avilla
url: https://www.cjav.dev/videos/rails-scaffold-deepdive
youtube_url: https://www.youtube.com/watch?v=j7Qh-wIo5Zc
youtube_id: j7Qh-wIo5Zc
embed_url: https://www.youtube.com/embed/j7Qh-wIo5Zc
thumbnail_url: https://i.ytimg.com/vi/j7Qh-wIo5Zc/hqdefault.jpg
type: video
---

# Rails scaffold deepdive

*Published: August 09, 2021*
*Views: 5424*

## Watch

[Watch on YouTube](https://www.youtube.com/watch?v=j7Qh-wIo5Zc)

[![Rails scaffold deepdive](https://i.ytimg.com/vi/j7Qh-wIo5Zc/hqdefault.jpg)](https://www.youtube.com/watch?v=j7Qh-wIo5Zc)

## Description

Learn all about what you get when generating a scaffold with Ruby on Rails. This covers many Rails conventions that follow the happy path and are often sensible defaults.
#rails #rubyonrails

## Transcript

what's up welcome back in this episode you'll get a deep dive into all of the fundamentals for building a very basic blog application this is like the bread and butter of rails this is like one of the one of the first demos that uh dhh ever did was to create a blog application super fast we're going to actually do it super slow so we're going to go through in excruciating detail not excruciating it should be nice i hope it feels good it's not supposed to be excruciating we're going to go into some detail talking about how you would set up just a very simple controller and model to add some to add posts to a rails application so we're going to start from scratch in this episode we're going to build just the posts and the controller actions for those how the routes work talk about the models a little bit of model validation and then in the next episode we'll go through the process of building custom authentication talking through all of the pieces of how someone might put in a user or password and then authenticate so let's start with a brand new rails app so we're going to say rails new blog here and we'll say dash t and we'll say database is postgresql okay when you start a brand new rails application you're sort of building from a template so i'm using rails 6.1.4 that is the latest as of today and it's going to install a bunch of gems which are libraries that we're going to use that have some you know they come with a bunch of logic that we can depend on so what we're going to start with today is we're going to use rails scaffolds we're going to say rails g scaffold and we're going to scaffold out a blog post application all right we're going to change directory into blog all right so rails is fully installed the next step we need to do is create the database so i can say rails db colon create and hit enter this is going to run the create command that will create the database for both development and test so we just created two databases one of them is called blog underscore development the other is called blog underscore test and when we create models and migrations those migrations will run as sql commands on those databases to create tables or update tables add and remove columns etc so that we have some some structure to work with so what we can do with rails is we can say rails g scaffold and post so we're gonna we're gonna tell it that we want to rails generate a scaffold and the thing that we're scaffolding the object in this case or the class in this case is called a post and our post is going to have a few different attributes it's going to have a title and a description so we can say title and by default if we give it any columns if we don't specify the type of the column then it's going to use i think it's just going to be like you know like a short input text or a varchar 255 or something like that in the database so it's basically just a string value and for the description we actually want to have maybe like a you know a text field that's going to contain more than potentially more than 255 characters so we want to say colon text this is how we can specify the type of uh of column that we want and by doing this just just by running rails g scaffold post title and description it is going to create a migration which will run the sql commands to add a new table to the database so this is the new migration it's going to add the sql commands to create the new table in the database with title and description it's also creating a new model and this model will be a class that represents instances of posts or relates directly to sort of the rows in that table so an instance of a post will have a title and it'll also have a description and there's a bunch of handy methods on these models on active record models that allow you to like find all the posts or delete a post or add a post it will also create these routes so it's going to define a bunch of routes for us and routes are sort of the paths in the url that map directly to functions that we're going to write inside of our ruby code so that when we go to a certain url a specific function is called and some html is returned and those functions are defined inside of the controller so we have a posts controller and inside of the post controller when we use scaffold it actually builds out all the default seven controller actions for us index show new create update edit and destroy those are all the seven actions that it will create for us scaffold will also create all of the different html files for us and inside of these html files we'll see that these views are going to use a little bit of embedded ruby that's why these are called erb h.html.erbs we're going to have some html files where we're writing just a little bit of ruby code in there to generate the html we're also going to get a helper i almost never use these helpers but they're modules that allow you to write methods that work inside of these views inside of the html.erb it's also creating these j builders so a jbuilder is a tool for writing ruby code that spits out json so we'll take a look at that in just a moment finally it also is going to create some scss files for us so we can style those posts so let's take a look at what this might look like so we can actually just say rails server or rails s for short and this is going to fire up the server this is going to start a server which is now going to listen on port 3000 so we have a server running on localhost port 3000. i can actually just command click on that inside of my terminal and we see oh when we open the page we see that we have a pending migration error so that means that we need to run our migrations let's go back to the terminal rails db migrate we have to run railsdb migrate to actually execute those sql commands that were created by our migration file when we're executing those sql commands things are going to change inside of the database in this case we're creating a table so it wants to make sure that we don't have any pending migrations that have not run and have not modified the database before we can actually load our server so we say rails s again we're going to restart the server here and we can click on this again we're brought back to the browser and it says yeah you're on rails so cool but we don't see anything about our posts and that's because these are going to be at the slash posts path so i can go to slash posts and this is going to be the index route or the route at which i should receive the list of posts back from rails and you'll see it's already got like a little bit of html here it's got a view for us this stuff up in the top left is only available in in development and it's kind of just giving us a little bit of sort of debug mode tooling you can kind of see some of the stuff about the request and drill into it usually this might be helpful if you're trying to debug some some performance things but what's really cool is that we can click on new post and we've already got an input form for a title we've already got an input form for a description so let's just say this is going to be a test post and we can click on create post that will create a brand new post and you'll notice that we were redirected to posts slash one so this is the show page for a post where we can see the title and description probably not exactly the way we would lay out an actual blog but it gives us the data and then we can go kind of modify the view and play around with it so now if we go back we have buttons here for or so this is the index view again where we see the list of posts and we now see links next to in this row for this post that can we can go to the show page for the post we can edit the post so if we wanted to say like okay this is you know edit added new content and we say update the post now we have this new content inside of the post we can go back to our index route and we can also destroy the post so we can just delete the post and we get this little pop-up that says are you sure yes and at the top we see a notice that says the post was successfully destroyed let's go back to new post if we wanted to create a post right now uh with out a title or description we could just click on create post that'll create the post so by default there's no there's no validations but we do get a pretty rough structure for what we would want inside of inside of a really basic blog application another thing that's really interesting let's say that we want to say like let's go back to actually like the posts index we're going to say we want to create a new post this is our latest uh post and we'll say create post now on the show page we can see slash post slash three now by default we're getting back because our browser is requesting html the server is sending back html so if we look here in the server logs we see that we received a request for uh slash post slash three that is the same route here slash post three and uh down here below we see that we processed uh this request with the posts controllers show method that's the show action inside the post controller as html okay so what that means is that inside of the post controller it's going to use the html views for that show route in order to render back the html that's coming back in the browser so if we look at this page here and we say inspect and we open up our network tab and let me make this a little bigger so three here is actually the request that's going for posts so uh in the in the chrome developer tools so you can sorry i did a little fast if i right click and go to inspect and then go to the network tab inside of these chrome developer tools you can see all of the different network requests that are going to fire from the browser to the server so we can refresh the page here and we'll see all of those requests head out and we see one at the top this is for slash posts there was like a request to pull in some css some javascript some more javascript and ico file for this little little earth thing that's happening up there we've got some more css and javascript and then we actually do see some results here so if we look at this request for slash three and we go to the response this is the html that is being rendered by rails back to the browser and the browser is interpreting that html and showing us what's on the screen super cool now another thing that you can do with rails and when using scaffold is you can actually append another format to this url so we can actually say json here and hit enter and we will get back the json data for the post so it's a little tricky to see i don't have like a chrome extension to make this pretty looking but we see that the id of the post is three that the title of the post is this is our latest and the description says post we also get created at updated at and a url property for the post so or the or yeah the url property for the post so this is actually can be pretty handy if you're building like a mobile client that's in addition to your um to your web web client but that is by passing in the format now if we go back to our server log here we see we started the request for slash post slash three dot json so that dot json is going to be interpreted by the controller or by the the by the middleware that's part of rails and it's going to pull off that json and say the format for this request is json and so here we see that we're processing this request with the post controllers show method again but now it's as json so we're going to go look in the controller in just a bit and see how this works but you'll notice that the difference is when we made a request for slash post slash 3 without.json the default was html and we got back the rendered html and it used these html.erb templates to render that back to us now that we're using json we're seeing that the json.jbuilder templates were actually what was used and that's what got spit back to us so all right let's go take a look at how this all works so we're going to change directory into blog again and we're going to open up the app controllers posts controller so actually let's go let's go to the routes first routes so we're going to go to the routes resources posts so just by saying resources posts this is important that this is plural and this is also plural there is another way that you can do this and say resource post where resource is singular and post to singular if you have uh objects inside of your database where there are really only one or you're only working with one this might be like your profile or your you know some sort of settings page or something uh or you know you only have one way to log in so you might have resource session instead of sessions basically if you do resource post you will get all of the the member routes or you'll get routes that look like member routes for working with an individual object when you say resources posts you get the index route and you get a number of other things that make it work with a collection of things this is the most common you're gonna have resources comments and resources likes and resources users and resources whatever just to uh to build out all of your routes for your application and so we've got resources posts this is going to create seven different mappings between routes uh http methods and actions inside of controller slash info slash routes okay so re like if you go to slash rail slash info slash routes as part of your url you'll get this html page which tells you all about the routes typically you could also or like in addition to this you could also run rails routes in the terminal but the output is a little tricky to read so what's nice here is you can see all of the different routes that are available to you and these ones at the top were the ones that were created by resources posts so we get the posts path that's going to be a mapping between the get request and slash posts and that is going to hit the index method or the index action inside of the posts controller we also the posts path also works for uh a post request so we can send a post request to slash posts also this is the http verb not like the blog post so this post is not blog post we also can send a post to a mailbox or whatever but like this this post method here is not the same as a blog post this is the post type of http method or hdv verb and we can send a post request to post that's how we create a new post and that maps to our posts controllers create action to create a new post all right let's keep going we've also got the new post path this is where we'll be able to create new posts this is the route that will return the view with the form for creating a new post we also have the edit route so slash post slash colon id slash edit so why do we need that colon id inside of the path well if you think about it when we're trying to edit a post we need to know which post we want to edit in order to know which post we want to edit we should pass along the id that matches the row in the database for the specific post we want to edit and so in this case we're passing along that id in part of the path for posts and so we can go to like slash post slash one slash edit that'll edit the first post in the database slash one slash three slash edit that'll edit the the post in the database with id3 and by edit here this is a little confusing when you're when you're just starting out so slash edit slash slash edit this edit post path receives a get request to this path and the server is going to return the form for editing the post so this is not actually going to change the post this path is not how you change the post this is the path that's going to return the form that will allow you to uh it's going to have the form fields that are like pre-populated with the posts data that allows you to edit that post all right next one we've got slash post id that just shows you the specific blog posts page and here we have patch put patch input okay you'll notice here that both patch and put have the same path they both go to the same path they also go to the same controller action so there are there's like sort of lots of arguments in the community about whether or not you should use patch or you should use put so these are two different http verbs one of them put means that you're going to replace the entire remote resource so you're going to like replace the entire post you're updating and you're sending everything about the entire post and you're completely replacing it with whatever you sent in patch means i am going to just change part of the post so maybe you're just changing the title or you're just changing the description so there's a lot of arguments about whether or not you should use patch versus put and it turns out that in practice it really doesn't matter whether you use patch or put as long as you're actually like updating the thing correctly and so both patch input both map to slash post update and so this is um this is how you actually send a request with all of that data that you filled into the form so when you hit submit it's going to send all of that data back to the server and the server is going to receive it and it's going to say okay i know which post we're going to edit because that that id is in the path and so it'll look up the post in the database we'll take in those new parameters that were sent to us as part of that form submission and we're going to update the post in the database so that it is has new values finally down here we have a delete request to slash post id this is going to call the destroy action on the post controller and that will just delete it from the database plain and simple sometimes you'll you'll implement your destroy action so that it actually just like marks maybe it just updates a column in the database that says archive true and then by default you just won't return those posts because you may not want to like always delete all the data from the database sometimes you do sometimes you don't there's there's ways you can implement this but by default usually you're just like deleting it from the database so those are all the routes that are created for us by resources let's keep going so back over here in slash posts oh yeah let's let's head back into our posts controller posts controller okay so at the very top here we see that the posts controller is inheriting from application controller so the applicant application controller is sort of like the overarching ruby class that's going to give you the ability to write methods that apply for all of your application you might you know create another controller that inherits from application controller where you can write your logic for maybe an area of your app so maybe you have a dashboard or you have like a marketing app or you have like your documentation page or your api controller and those might apply different settings for what happens when you receive certain types of requests it might do some sort of authentication or some other things but for now this is the default pattern we're going to just inherit directly from application controller and we'll go look at application controller later next what we're saying is before any of these actions are called so before index is called or show or new or edit any of those routes are called and again these are the functions that are going to map directly to those paths and http method combos before any of them are called we are going to execute a method called set post only on show and then you can specify only on show edit update and destroy so this before action there's a couple different ways you can write it so you could write it just like this where like you only put before action set post then it will run before every single action or you can say before action and then only on these actions so now what we're doing is we're saying before uh show edit update or destroy so before this route or this route or update or destroy we want to call setpost so set post is typically or your before action is typically a method in the same controller so let's go look at set post so set post down here is saying uh find we're calling post dot find params id this params object is a is a ruby object it is a its type is hashed within different action different access doesn't really matter it's basically a bag full of or yeah you can think of it sort of as a bag full of all the stuff that was passed to you in the request it could be um there's going to be keys in here that are related to the keys that are mapped between the path the the dynamic parts of the path uh there's also going to be the keys in here for the the key value pairs that you send in the post request or in the query string parameter so the params object in this case when we say params id we are looking into this params object which again is all the stuff that we were passed in the request in either the path the query string or the post body and we're reaching into it with id in this case colon id this id property is going to be set in the path and recall back from our from the routes over here that this colon id was in the path and that colon id is not ever going to be passed as just colon id in the route we're going to pass one or three or five that's going to be the id that maps to the the row in the database right and so here what we're doing is we're saying post.find we're passing in the id so this is going to do essentially select star from posts where id equals whatever we passed in so let's take a look at that so if we come back over here and we go back to like post slash three and we look at our um if we go back to the server log now we can actually see this happening so we see uh when we went to slash post slash three that three mapped to colon id and when we called set post that post dot find resulted in this query in this sql query so we're seeing select posts posts.star or select star from posts where posts.id equals the first parameter limit some other parameter so and then we this is like the params that are being passed in so we see that dollar one that's going to be our the first argument so we're saying like select star from posts where post id equals three limit one so just give me back one of them so that's what post dot find is doing and that is the result of set post and we can actually see this super helpful little arrow that goes down and tells us this is on line 62 in the posts controller and the method that it's calling is setpost so we'll head back over here line 62 in the posts controller and this post.find so that's what's happening and what's being returned from that sql query is going to be some data that is going to hydrate or sort of like fill up or create an instance of a post object so a post is a model we'll go look at that class in actually right now so let's look at the post.rb right now it is a model it looks super simple there's nothing in there there's no there's no right now we don't we haven't defined any methods we haven't defined anything inside of post but because it inherits from application record it is able to look at the database and understand things about itself it knows that because its class name is post then by default its table name in the database is posts all underscore and it knows that because it's inheriting from application record that it has um you know those columns in the database and then based on all the columns that are in the database it can sort of use reflection or it can sort of know like know that it has methods on it for the title and description and also the id and some other things for the timestamps created that update that etc all right so we're calling setpost before any of our methods are called and we're storing the result of that which is going to be an instance of a post object in the at post instance variable all right so that's what's happening with this before action here so before we call our show edit update or destroy all of the things if you think about it that are about an individual single post so before any of those happen we're going to call setpost that way we have access to this instance variable called at post anywhere inside of this controller i'm sorry anywhere inside of any of these methods all right let's go to the next few lines down here so the index route so if we receive a request to slash posts or slash post.json we are going to um make another database query post dot all is basically select star from posts and then it will hydrate uh a an active record collection which is a fancy basically it's just like a supercharged sort of array or collection that gives you a bunch of other methods and that al that collection is going to be stored here in this app posts instance variable and we don't actually see any other logic inside of the index route right so rails is using a lot of convention and a lot of people would say that it's very magical and when you learn a few of these different conventions then you can become very very productive so inside of this index route by default if we don't specify anything about which views to render or which templates to render we're not doing any sort of logic inside of here so by default it's going to render the view that matches the name so in this case index we're going into the views the views directory the posts directory because this posts directory maps to the same name of the controller posts right and it is going to use the index.html.erb template by default if nothing else changes you'll also notice that there is index.json.jbuilder and rails is smart enough to know that if you receive a request that's json give back to json so if we look at this let's actually go to slash posts and hit enter this is the html we're getting back this is index.html.erb and we can look in the server log here and we'll see our our database query selects star from posts and that is rendering our index.html.erb template on line 15. that is just like all implicit it just knows that it needs to do that now if we say dot slash posts dot json we get back the json and it just knows that because we are passing this format json then it should default to using jbuilder now the database queries are all going to be exactly the same because that index action that it's mapping to is not changing so it's going to you know first it will you know do select star from from posts and then it's going to render the index.json.jbuilder let's actually look at so this is the index.html page that scaffold created for us at the very top here we have a notice this notice is going to spit out things that we just want to show maybe like one time basically it's kind of like a a little reminder of what's happening so for instance if we come back over here to slash posts and we hit destroy and yes for sure post was successfully destroyed this bit up here we can actually right click and inspect and look at the html and we can see that post was successfully destroyed is inside of the paragraph tag with id notice and if we go back to our index.html.erb we have this paragraph tag with id notice and we're printing out the notice so this is erb syntax this is embedded ruby syntax so we're spitting out notice so this notice variable is just available to the view if anything has been passed as part of a notice all right next we've got a h1 with posts it build it or it built out the entire table for us and if we get down past the table head we have the table body here so it's actually iterating over all the posts again here we're encountering embedded ruby this time notice that we don't have an equal sign so this one had an equal sign this one does not have an equal sign the difference is that uh when we want to like actually spit stuff out into the html we're going to use the equal sign when we want to do logic for looping or conditionals we are not going to have the equal sign so here we are we are doing some logic we're not actually spitting anything out on this line specifically instead we are looping over each of the posts so recall that at posts was an instance variable that was set in the posts controllers index action and that is going to be all the posts and so we're saying like go over each of the posts and pass each post into this block and so when this block executes we'll have access to an instance of the post here we are using the equal sign and we're saying okay at this point we want to like actually spit some stuff out into the html and so we're taking post.title for the post and we're printing that out into the table data at that point same thing for the description on this third table data we do something a little different we're using a link two so link two is a ruby method it's a ruby view helper it's a helper method that is going to take in a couple different arguments and return some html as a string and that will be rendered back as the value that's entered into the html that we're returning from the server so for the next three we're creating links one is a link to show edit and destroy destroy is a little bit fancy here we're actually specifying the method and we're passing in some other stuff here so we've got a confirm call confirm is remember when we destroyed that one post we got the little pop-up that said are you sure you want to destroy this and we were able to say yes and that actually destroyed it so we've got destroy and yeah so this is this is the html that's being rendered back for that index route let's take a look at the show route the show route doesn't actually have any logic inside of it right we're not doing anything inside of here there's no render this render that there's no instance variables or anything that's because this show route is depending on the set post being called so that it can use that at post instance variable we talked about before talked about before so this is this is running and that instance variable is going to be used inside of the implicit template that's returned so show.html.erb so this is going to be the html version this is going to be the json version again we have a notice we've got the title this time we're using the we're again we're spitting it out we're using the equal sign to print it out and we're using at post so that's a little different from the index right so here we used at posts plural because that's a collection of posts but then inside of the block post here is not an instance variable it's just like a local variable that's local to this block that's available inside of inside of the template so now we can just use erb to print out the um the you know attributes of that instance of post but inside of show hopefully i'm not confusing here inside of show we're using app post directly because the show page again is working for an individual post not a collection of posts let's keep going so the next action here is new we are creating a new instance of a post that is going to be an empty post and we'll talk about the purpose of that in just a moment edit same thing as show it's just going to send back this the edit page and the edit page is actually very simple and it has something another thing that's interesting that we can talk about and that is that we are calling this render method inside of the template and this render method is being used as part of again erb where we're going to like render out some html and this is actually called a partial so we're going to render the form partial and we're going to pass it some data so this is like saying like render a sub component of the html so render just like a sliver of the html back and give it some data and the data we want to give it is this post and so when we render the form partial we'll go look at that in a moment it's going to receive as an argument this post this post variable that we can then use inside of the form partial so this inside of our views down in views posts we have underscore form.html.erb this underscore that's in the front this tells us that it is a partial what's weird is that when you say render here you don't actually say like render underscore form or anything you just say render form and it knows that you're rendering a partial and that that partial's name is actually underscore form.html.erb so if we look at form form is saying we're going to create a form we're going to use the form with helper and this time we are going to spit out because it's going to spit out a form tag that wraps the entire this entire view basically and the model that it's using is post in this post model again was the argument that was passed in to the partial so post here this post is going to define that local variable that refers back to the instance variable at post okay inside of the form partial we actually have a whole bunch of logic here for creating these fields displaying a bunch of error messages we'll talk about this in more depth later i actually don't use these form helper methods like form with and form dot label form.text field because it is challenging to move to migrate from a form that's built with form with to another framework if you're going to switch to a client-side framework like react or angular or svelte or view or ember or back like any of these front-end frameworks you're probably going to want to work with just bare html and so i usually write all of my forms with just raw html there's a couple other things this gives you one is called an authenticity token and that's to prevent cross-site request forgery or the ability for someone uh to send a post request from a completely different server to your server to like create something um so that this form with helper is going to give you a lot of stuff we're going to talk about that in uh later we'll talk about that later okay back to our post controller that is our our edit our new and edit actions they're both going to use that form partial one of them is going to pass in a an existing post one of them is going to pass in a new post so when you see the new page all of the fields are empty but there is values in there the values are just empty values for this blank post basically so post.new is creating a new instance of a post that is just empty it's not stored in the database when we say dot new that just creates a new instance in memory it doesn't actually persist it to the database but what does persistent to the database is the create action so this one is a little bit more involved let's talk about how this works first we're going to call post dot new and we're going to pass in post params as our argument so where does this post params thing come from and how does this work and what's actually happening right here well we're calling post.new which does not actually persist the post to the database and we're passing in post params and post params is going to be another method that we write in the same controller by convention and that's down here at the very bottom post params and here we're saying params.requirepost.permit title and description so again we're talking about params remember that we talked about params earlier how that's sort of a bag of all the things that you receive in the request one of those things is going to be any of the the dynamic arguments that are part of the path or the query string or the body whatever so this is going to be where we re where we deconstruct the params that we received in the post request and we say okay we must receive in the post request or the put request or patch request we must receive an argument where at the top level there is the key post so we must receive at the top level the key post so let's actually go and create another form so we're gonna say new post title is uh testing testing is this thing on and we're gonna hit create post when we hit create post actually let's inspect this too so this is our form the form action so this is uh the form builder built all of this html for us right and notice that it has the authenticity token here we'll come back to that that's again for protecting against csrf or cross-site request forgery the action for this form tells it where to send the data so we're sending a request to slash posts and the type of request we're sending is a post request i'm realizing that post blog post was a bad example because there's so many post post posts this post request is the http verb not the like type of post so this would be um you know get post put patch delete etc so we are sending a post request to slash posts and the data that we're sending is going to be what is collected in these input forms so the name value is what's important here this name value defines what ends up in params in the controller so when we click on create post that's going to like collect all the data from all these different inputs and it's going to send it to our server and when it sends it to our server it's going to send it and the values so testing the value testing is going to be nested under post title and the value is going to be testing so there's going to be a top level sort of hash where we have the key post and post is going to point at another hash a nested hash where the key is title which points at a value and the value is testing so it's going to be something like this we're going to have like post and post is pointing at another hash where there's a key title and title is pointing at our value testing and it's going to have some other values too because if we look at this field we have the description so post description so this is going to be a description and that's going to point at this giant thing that i'm writing right now let's just say thing on is this thing on okay and that's going to end just like that so this is kind of the the shape of the data that's going to come into rails and hopefully this makes sense yeah so this is what we're going to receive as part of the post request now when we're looking at the params and we say params.requ so okay what else is it going to require it's also going to have maybe like the action is going to be index or yeah create right and it might also have a controller post posts controller or something like this right so it knows that it needs to go to the posts controllers create action because we are sending a request to slash posts with a post http method when we say require post here when we say params.requirepost what that does is it looks at all the params and it says you must have this post key and when we say require it actually just kind of like strips other stuff out sort of so you can kind of think of it as doing this basically so that you only have title and description left and here where we're saying permit permit title and description we're saying that title and description are okay to set on the model that we're creating or updating and the reason you might do this is consider the case where you have like an order right and you want to allow the user to create a new order and they're going to say i'm buying a i'm buying a car the id for the car is f-150 and the value of the car is 50 000. and i'm this is me submitting my order now in your database if you it is a very simple very simple use case right if you're in your database you were like okay i just have to look at the orders table and then in the orders table i'm going to look at the paid column and if this person has paid for their order i'm going to send them their their goods so if you were a hacker and you wanted to try to mark your order as paid you might mess around just in the html here and right click and say oh i'm going to actually like edit as html and i'm going to add my own input field that is going to be like type of you know i don't know text and i'm going to say the name is order paid and the value value is equal to true and i'm just going to like or maybe even make it like hidden and and that's it now there's like a hidden field so when i submit this form which we'll do right now right and uh we look at the server log we received a post request here so uh we received a post request to slash posts and we got the authenticity token we got our post and we also got order paid so like anyone can just right click inspect edit the html that's on the p on the page and send whatever the heck they want in and that is why we need this permit thing because anyone can just edit the page and say they can pass whatever they want and if order if we were saying params.require order.permit uh you know title order id and paid then anyone could just go in there and mess around and pass in whatever values they want and sort of like decide that they have paid even though they might not have actually paid for this f-150 and they would receive the goods which might be kind of nice but permit here this is so this whole this whole deal with params that require post.permit title description this is called strong params i think it was added in like 20 13 14 15-ish before we had strong params you had to manually go to the model which was like really far away from the controller and set up a bunch of permissions allowing certain things to be set on the post or set on your models so this brings it up into the controller and the whole purpose here is so that only trusted yeah so we only allow a list of trusted parameters through when we're creating or updating our data okay also worth mentioning you might have different parameters for create and update like maybe you can create a post with a title and description but you can't update the title you can only update the description in which case you would have different methods for post params in in each case all right that was a long way to to talk about this one line here okay so we're going to create a brand new instance again this does not persist it to the database it just creates a new in-memory instance that has a title it has a description and that's it then we get to this block here where we're saying respond to do format now respond to do is taking in a block and that block is going to pass the format this format value was passed in from localhost 3000 slash in rails info routes yeah so this recall that this like colon format is here right so when we have parts of the path that are inside of parentheses this means that it's optional um i can't remember all the computer science terms for this it's like a you know grammar expression something something but this this means that it's optional so you can optionally pass a format and notice how the format starts with a colon similar to id starting with a colon and that format notice also that the dot is before it that's because when we say like slash posts dot json the dot part is not part of the format dot json is not the format the format is just json without the dot so we have we can optionally put a dot and then the word of the format after it anyways this format is going to be available here when we say respond to do format and what format allows us to do is specify different responses based on whether we receive an html request or a json request or a turbo stream request or an xml request csv request there's tons of other different formats that you might want to support so that's what this block is doing it's saying like let's set up a block where we're going to either do something based on one type or another type of response if you're building just a web application that doesn't have json you might just ignore this entire line and just redirect to post or whatever do the stuff that's inside here if you uh otherwise you might want both you can you can do as many as you want to all right if at post dot save at post recall at post is an instance of a new post it has the title and description passed in from the post request from the body uh and we're calling dot save we are not calling dot save exclamation point or dot save bang here dot save is a method on active record base or act this these active record models that when we call it it returns a boolean value so this tells us true or false this just tells us yes we saved it in the database or no we did not save it in the database and if we saved it in the database this will return true and then we'll do this block of work if we did not save it in the database it'll return false and we'll do this block of work so in the first block of work here we're saying if the post was saved to the database because it is completely valid and it didn't have didn't you know fail any database constraints there's no you know foreign key issues and it passed all of our validations that we've written for the post like maybe we might want to add a validation that required that it had a title and that the title was longer than x and that the title was unique and that the title didn't have bad words and the title had emojis i don't know like you could you could write validations that checked all of those things and if any of those validations failed this would return false and we would come back over here and return some other stuff otherwise if it successfully saves in the database and we received the request as html we are going to do this we are going to redirect to app post so redirect 2 is a way of telling the like is it's a way to respond to the browser with a specific header and http status code that tells the browser like okay got it we were able to create the post thanks so much here's a new url go request this new url and the url is going to be slash posts slash the id of the new post so this is actually saying like redirect to uh posts uh post path for app post dot id which is the same as like slash post slash plus like at post.id but because it's so common that we want to redirect to like the show route for an instance of a thing instead of having to write all of that you can just write at post and rails will figure out like okay we're redirecting to this class what class is it okay it's a post class okay what is the path for the post class then it's going to look up the controller and the routes and everything and it'll figure out that it needs to go to slash post slash the id of the post this bit that's after this notice notice that we're getting back to the notice recall that in the index.html.erb page we had like that little render at the very top that had the notice that's where we're going to spit out this content so this is how we assign that notice variable that's going to be used when we when we make that request this the like the implementation of this under the hood i don't actually know how it's implemented it might be cookies or something but it doesn't really matter it's just a way to pass that notice variable to the view and redirecting okay if we receive this post request for to create a new post as part of a json request so maybe this was happening with an ajax call or we implemented this with an ios app or something where we're going to like make a json call to create the post we don't want html back if we're making the call from an iphone app so here we're going to render show so we're going to render the show template for a post which is going to be the the json for that post and the status code we're going to respond with is that created status code and we are also going to pass along the location of the post so if we wanted to we could receive or retrieve the instance of the post now if saving the post failed we're going to re-render the view the new view and that new view recall that new view is rendering the form partial perform partial that's here that new view when we render that new view we're going to also render status unprocessable entity aka 422 this just means like so there's a there's an important piece here though so let's go look at the new view real quick the new view is rendering that form partial just like the edit view so the new view and the edit view are very similar one of them has a link back one of them has a link to the show for the for that instance of the post the new view doesn't have a link to show because there is nothing to show for a post that hasn't been created yet but notice that we are still passing in the post now if you think about like why we would pass in the post for the new view uh and that is because we want to make sure that if someone messes up their submission we are able to repopulate and rehydrate those input fields with whatever they had filled in that was valid so for instance if we were validating that they put in a title and a description and that the title had emojis in it and they filled out the title and they spent hours writing their description they hit submit and we were we just responded with an empty form where the title and the description were empty and we said invalid title they would be like ah their head would just explode because they would be so frustrated that they had typed in this description i'm sure you've experienced this right you go to some page you're working on this you know i don't know peer evaluation or something right or you spend a bunch of time filling in a form and then you go to submit and there's a some tiny little thing that was invalid like oh you accidentally mistyped your cvc for your credit card or something and then it wiped out the entire form and you were just like raging because the data that you had saved that was completely unrelated to the form field that was invalid was also wiped out so the whole reason that we passed that instance variable down from the new view is so that if this post this instance variable post had any valid data in it which it would have when we created it right it would have had the description and the title those would go back into and fill in the input fields so that's not gonna like keep this post around between requests this is all like um it's not persisting between requests as we're working through like fixing uh fixing a post that was invalid but it is going to just keep the data keep passing around the data so that your form stays you know filled out basically all right long-winded go down to update update it's basically the same exact thing as as create except we already have an instance variable for the post which was created by set post down below we're calling update instead of calling save and we're passing in post params again that's going to do the strong params business where it ensures that there's a post there it's going to require post and then permit title and description and then we're going to do something very similar here where we redirect to the post if it's successful or we're going to we're going to render the edit view if it's unsuccessful the one other thing we can talk about is the errors so if we if we fail for either the create or the edit action we're rendering back the json for the errors now when you write active model validations active record validations for your models those are going to automatically create this errors object if it fails to save to the database and you can get really nice beautiful error messages from just like a couple of simple methods inside of your models and we'll look at that later so that is our update route let's go down to destroy we're just calling post.destroy if it was uh and that's it we just called post.destroy deletes it from the database and we move on if we got the request as html we're going to redirect back to the list of all the posts and we're going to add that notice that the post was destroyed otherwise if we got the request with json we're just going to render back and say ah cool sounds good nothing nothing happens so we're actually responding with just a header with that has like no content um all right that is the entire controller action we talked about routes we talked about the controller we looked at all the views this is what happens when you use rails g scaffold so i hope that is valuable let's actually break for uh for the next episode what we're going to do is implement our own authentication so we're going to implement um just username and password or email and password authentication with rails from scratch walking through every single step in the process and yep so i hope you will join us for that next episode thank you so much for watching i know this was super detailed this was really intended for folks who are brand new to ruby on rails and yeah so follow along in the next episode and we'll talk about a lot of the fundamentals for authentication and how those work thanks so much for watching and we'll see you next time

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