--- title: Fun with Rails Generators slug: fun-with-rails-generators published_at: 2023-10-06 11:00:07 +0000 updated_at: 2026-03-04 20:12:55 +0000 summary: description: We'll hack on the api_client generator that comes in Jumpstart Pro to learn about rails generators. Come work with me! - https://www.ycombinator.com/companies/craftwork Rails generators guides - https://guides.rubyonrails.org/generators.html Jumpstart Pro Rails - https://jumpstartrails.com/ Thor - http://whatisthor.com/ https://github.com/rails/thor Model Generator Source - https://github.com/rails/rails/blob/main/activerecord/lib/rails/generators/active_record/model/model_generator.rb Named Base Source - https://github.com/rails/rails/blob/main/railties/lib/rails/generators/named_base.rb#L182 Generated Attribute Source - https://github.com/rails/rails/blob/main/railties/lib/rails/generators/generated_attribute.rb#L72 #rubyonrails #ruby #rails tags: [cjav_dev, web development tutorials, web development for beginners, vim, ruby, rails, javascript, ruby on rails, active record, ruby on rails tutorial, generators, rails generators, thor] views: 1089 author: CJ Avilla url: https://www.cjav.dev/videos/fun-with-rails-generators youtube_url: https://www.youtube.com/watch?v=8Rnf_-vDuaU youtube_id: 8Rnf_-vDuaU embed_url: https://www.youtube.com/embed/8Rnf_-vDuaU thumbnail_url: https://i.ytimg.com/vi/8Rnf_-vDuaU/hqdefault.jpg type: video --- # Fun with Rails Generators *Published: October 06, 2023* *Views: 1089* ## Watch [Watch on YouTube](https://www.youtube.com/watch?v=8Rnf_-vDuaU) [![Fun with Rails Generators](https://i.ytimg.com/vi/8Rnf_-vDuaU/hqdefault.jpg)](https://www.youtube.com/watch?v=8Rnf_-vDuaU) ## Description We'll hack on the api_client generator that comes in Jumpstart Pro to learn about rails generators. Come work with me! - https://www.ycombinator.com/companies/craftwork Rails generators guides - https://guides.rubyonrails.org/generators.html Jumpstart Pro Rails - https://jumpstartrails.com/ Thor - http://whatisthor.com/ https://github.com/rails/thor Model Generator Source - https://github.com/rails/rails/blob/main/activerecord/lib/rails/generators/active_record/model/model_generator.rb Named Base Source - https://github.com/rails/rails/blob/main/railties/lib/rails/generators/named_base.rb#L182 Generated Attribute Source - https://github.com/rails/rails/blob/main/railties/lib/rails/generators/generated_attribute.rb#L72 #rubyonrails #ruby #rails ## Transcript so one of my favorite features of the jump start Pro rails starter kit is the ability to generate an API client so you can say rails G API client open aai this is the example and this generates a a client for you and also a test now a client is really just a class with a set of um methods that are in here for making API calls to a third-party API so you've got your standard stuff that you would build if you were building your own API wrapper and this is all really common stuff that you're going to build in most applications that integrate with third parties and what's cool about this is that the application client wraps up a bunch of HTTP methods and handles pagination and a bunch of other things for you automatically really handy and we are integrating against tons and tons of different apis at craftwork where I'm working right now and maybe that's to pull some messages from from twillo or from a chat service that we use called Podium or if we're pulling some information down from some rapid API a apis for property data Google Maps directions etc etc we're going to build little API wrappers so there's a couple different options when you do this right like you could either install the official thirdparty client which we are using stripe by way of the pay gem in this application or you can write your own API wrapper and what I like about writing your own application client is you don't have to worry about dependencies right because your third-party implemented Ruby rapper might have dependencies on some other HTP client or something so it's easier to keep up to date number two you sometimes those libraries are pretty big and maybe they include hundreds of endpoints but you might only need to access one tiny endpoint and you're only going to pass certain parameters so it can be a little easier to wrap it up like this you also have a lot more control over the shape of the way that the client class works and things like that but one of the things that I wanted was I found myself generating this API client and then constantly coming in here and being like okay I actually don't need any of these and this is actually going to be called messages and then that sort of breaks all these tests because now we have to come in here and change like anywhere that we were saying posts we have to change it to m mesages and anywhere that we have this Bas URI now we need to change this to I don't know api. cjv dodev or whatever like to go and backfill all the different pieces so it gives you a good template but what I was hoping for was like something a bit richer and and following the pattern from rails I wanted to do something like rails G API client open Ai and open API or open AI has this completions endpoint where you can send a request to like api. openai slv1 completions and if you send a post request there it will do some open AI thing and give you back a completion so let's take a look at how this is actually generated I would definitely again recommend go bu jumpstart Pro for your next project let's also look at the API client generator here so inside of the API client generator it is using the rails generator's named base so this is is uh part of rail's generator system and there's actually quite a bit to how rails G works and the all the rails generators I find that using generators makes me move much quicker and really exciting there's also a bunch of stuff that's built into jumpstart we're not going to look at it but you've got like inbound web Hooks and some other things and then so the way that this sort of works is that when you call template it's going to use the templates that are inside of here this is just like how rails generators work and so it knows there's a couple of methods that you can call in here for copying files or replacing files and things like that and then file paths these are all part of the generators my sort of like fantasy-driven development was to say I want to do this and I want to have this completions endpoint there and I want it to be a create call and I also want to have the URL replaced now this named base thing under the hood is using Thor so if you're not familiar with Thor it's like this tool for building command line interfaces in Ruby so go head over take a look at Thor it's a really established gem for building command line interfaces and there's a lot of cool stuff here so the rails generators are built on top of that so we have this generator named base so if we look at named base inside of rails we're going to find this class here rails generator named base inherits from Bas and then yeah I don't know what does bass look like let's come in here and look at Bas okay base is now inheriting from Thor group so there's going to be like a bunch of commands basically that you can build inside of this named base what's what the named base gives you is when you say rails JG API client this open AI this is the name so by saying open AI it knows how to take this name and do a bunch of different things with it using active support inflections or whatever to make it underscore or make it camel case or make it whatever like all the different pluralized and singular and all that so the named base is so that you can pass it a name now there's things there's other things that happen in here one of them is that this parse attributes method is called if the class responds to this attributes thing and so if we look at parse attributes and also it took me like a little while to dig into here and figure this out you'll see that it's calling into this rails generators generated attribute. parse and pass passing in the attribute That's So when you say like rails G model thing you can do oh this has a name and that's a string and it has a description and that's text so there's several different ways that you can pass these in here but each of these are passed in as generated attributes so if we look at this generated attributes class you'll see that there is a a set of types so in the parse method it's going to split each of those ARG doents on the colon and it is able to grab the name the type and whether or not we said index and so there's a couple fancy things that happen here but one of them is that it checks to see if it's a dangerous name so it and it also checks to see if it's a valid type and valid type right now requires that it's the type that we're passing in is one of these default types which is one of this list right and for now if we wanted to update our API generator we could say rails G open API client we could say create completions string or something like that but this would have to be part of what is in the list of database things and I didn't want to do that I want to be able to like use I want to be able to use like my own stuff right I want to when parse attributes is called on my version of of this named base so this API client generator I want to use my own parse attributes method and this in instead of using the the default Types on this rails generators generated attribute I'm going to create a new class here and this is going to be class like API client method or something and I will have my own parse method that's going to take in some attribute and then I'll decide oh the methods that are available are index show create maybe update delete Etc and then when I'm parsing the attribute I can do the same sort of thing so I'll take like name and type is split on colon and now we can say if the type is not valid uh valid type so if it's not a valid type then we can raise an argument error so let's make this method valid type and this is going to take in the type and then that went too far too far GitHub co-pilot okay so we want to just see methods do the methods include the type two symbol and then we also want to check to see if the name is valid and if both are valid then maybe we'll initialize a new instance of this API client method so we'll have this yeah we'll have an initialize method that takes in the name sets the name and type and then maybe we have Adder readers for name and type so that when we new up a new instance of this API client method it will have a name and it'll have a type and so the type might be one of like index index show create update Etc and we could also check like is it a valid name or whatever but for now at least we've got like a class that we can use and then let's also look back at this parse attributes method again and so we're just going to copy what's already there and we'll paste that in but instead of using again instead of using this generator generators generated attributes thing now we can use like API client method. parse and that's should give us some attributes back now by default we're not actually doing anything with the attributes yet but that should get us a little closer so now if we just say rails G API client uh completions create let's see what happens okay we got an explosion now this is saying undefined variable or method attributes ah yes so we need to tell our named base about attributes so if we look in here okay so in the named BAS Base by default it does not accept attributes it just accepts the name which is that first argument we talked about but if we look at for example the model generator so I don't know where this is going to be let's just try to look for it when you're on GitHub you can just type T and it'll let you search around so model generator is that a thing model generator test okay H raise I should never be loaded okay so that's in the test fixtures so let's try this again model generator and it's going to be in live rails generators rails model that looks closer what does this models helper thing do okay that doesn't look right let's look at div record model generator is that a thing okay maybe here we go okay so this is the generator that's used for active record so part of I believe this is part of Thor we can say there's an argument called attributes and this kind of tells us about those attributes so we can copy this argument and paste that in now ours is going to be a little different instead of field type whatever this is going to be like the method name and then type or something or maybe verb I don't know like for the HTTP verb or something method name verb okay and then also we don't have a default now so we can do that type if type. nil we'll do like type is equal to index or something and then also we can do like type is equal to type to symbol because we were always going to want that to be a symbol probably so now we should be able to pass in attributes okay so let's rerun this and see what happens all right crashed again what do we got Adder dosit no method error split for application client API method blah blah blah so one thing I don't know why but this parse attributes method is called twice when you're generating I have no idea I don't know if that's like once for each template or whatever if you're a rails and then comment down below let us know what's up also quick break for our unsolicited self-promotion we are hiring we're hiring at craft work so if you are looking for a rails job you have rails experience we would love to hire some folks yeah hit me up and we'll get you connected with Mike craft.com to get in the pipeline and yeah let's have some conversations we're building some fun stuff in the Home Services industry starting with painting we got some some cool stuff we're building out so let me know if you want a job all right back to the regularly scheduled content here okay so if we call parse so if Adder is an API client method we'll just return Adder I don't know I don't know why yeah I don't know why it's built like that but that's something I found like as I was hacking on this stuff okay is there a conflict yes I'm just going to say yes yes yes regenerate them and let's take a look at our open API a open AI client all right so nothing changed right nothing changed but we do have or we should have some attributes now so what's cool is that these attributes will be available in the template that's used to generate this so now inside of the template let's just pretend here for a second that we're going to do attributes. each do adder and what can do is we can just say we can say Def and then add. name and this should generate new methods based on what we passed in um and then here we can say like puts hello Okay so this attributes array again is going to be generated based on the arguments that we're passing in here so we're going to say yes regenerate and now if we look at our open AI client now we have completions let's messy because my thing is telling us a bunch of stuff about new lines completions so we have deaf completions puts hello so this method is being generated based on what we're passing in what's cool though is that like now that we have this API method class here we can check to see things about the type so maybe we can check to see like let's see let's make these instance methods we're going to say is this a create method and the create is going to say is the type equal to create and if so in the client. rb. TT thing here we can say if Adder do create if it's a create API call then we know that we're going to do some sort of post request right because the in the example here create post it's a post request to the path with some body and the body is going to be the arguments that are passed in so in this case if it's a create call maybe we have some title something like this title body and maybe eventually we accept these sort of things too on the command line as arguments but for now this should get us pretty close now when we're when we're printing out the HTTP verb or method here we want some way to do that that doesn't map to the rails action names so maybe we have like method to verb and this is going to be like yeah index is a get show is a get create as a post updates a put deletes a delete update could be put or patch or whatever depends on your API maybe you have to go in and change that but whatever that's it's fine okay so now we can use this methodto verb constant to get a verb out based on the type right so now we can say add. verb that's going to give us this get post put delete whatever and then the method name is going to be slash and then Adder do name okay and then we're going to going to have some body and in this case we're going to have title is title and body is body and I know standard is going to yell at me about having these empty spaces whatever all right let's let's run this again completions create yes we want to replace it all right now let's go look at our open AI client all right super ugly right with all these dots that those dots are trailing Whit space so inconsistent trailing Whit space right now I have it so that on Save standard will rerun and reformat my page but but hey pause for a second and let's celebrate that we've got a method being generated which is pretty dope right and it's passing in the right stuff and like really I think we just need to add V1 which is like trivial to go back and add maybe eventually we make it so that it like maybe this needs to be like V V1 SL completions create and then we can figure out like oh here's we should actually call call it whatever we can do stuff based on the name or whatever but another idea that Chris Oliver had was like What if we had this so that you could do maybe Creations index and then pagination or something and that would add the pagination stuff to it there's a lot that we could do from here which is really cool okay so that's getting pretty close let's do a little bit of meta programming because this sucks right we don't want to write create every time and in our client we are going to have probably there's going to be a different shape for the method depending on if it's create index show etc etc and so I think following the same sort of rails conventions and rails patterns makes a lot of sense so here let's do our like methods each and then we're going to use Define method which is a a method in Ruby for us to dynamically Define a method by passing in a string and in this case we'll just say create question mark index question mark show question mark Etc that way we don't have to have this and we should get like all of those for free so I'm just going to say say let's grab those four lines and we'll make another one that's if it's an index so in this case we're not going to pass in any arguments in maybe we want some like query string or something but probably that's fine I would guess let's make a show method and for the show we're probably going to take in the ID right and this is going to be a slash ID depending on the API you might need an like a line at the end or a slash at the end some might not I don't know like whatever that's fine so now we'll do update so update's going to take an ID of the object to update and it's also probably going to take some arguments like title and body and these are really just going to be like examples right so that people don't have to guess the shape of what we're P like passing in here title title body okay and then I don't know what's the last one is delete or maybe destroy we call it destroy over here let's make this one destroy just so that it matches the rails the rails stuff okay and yeah that should have the delete method with the ID nobody so I think that gets us pretty close so we'll say rails completions let's do index completion show completion update completion delete and let's just see what happens crashed okay invalid type type which one did I oh it's destroyed we just changed that okay but now we've got like exceptions that are working and maybe we could look at it and say did you mean this if it was close or something I don't know or if they pass delete did you mean destroy or if they pass get or post did you mean index or create or whatever okay let's take a look at our open AI client all right super cool so we've got a list endpoint for completions completion with an ID completion this this is going to be our update method but what's weird is that now we have a name conflict right we've got a name conflict because we're saying completion and completion the other thing is that like sometimes apis will be weird and they might have I don't know comment completion and if we were to do that with capital letters like maybe the actual API requires that you pass Capital C and capital c but what's going to happen in our in our actual Ruby class here is that it's going to look very funky Ruby methods I don't know I don't know I just don't like Ruby methods to look like this another thing we can do here is we can write like what is our method name so method name and here what we can do is say name. underscore okay and then inside of here everywhere that we're saying name for the method name now we can say method name what that does is it makes it so that our API endpoint like the actual text that's being passed to the endpoint can still use that capital name because maybe that's what the API is actually expecting but our Ruby methods should be familiar so open AI client all right so now we've got this like comment completions thing that's underscored or snake case and now like the actual API endpoint looks the same but we didn't actually fix the name conflict here so another thing we might want to do is come up with a prefix and the prefix might be something like like if the type or if create right then the prefix is going to be create underscore and then at the end we'll do something like prefix plus the name right and then we might have else if the prefix is update destroy delete whatever this there's another way to do this that is something I picked up in Python that I like to do when it's when you're doing an a bunch of if else statements and it's also like instead of using a case block you can say say prefix is a dictionary and we're going to index into the dictionary in a second so here we might just say yeah if it's index a list if it's show find create update delete and then we can index directly into it right now with our type and we'll get back one of these prefixes and then instead of concatenating the string like this we'll use string interpolation here at the bottom so that we can join on underscore we could also have just done a join or whatever but this kind of reads nicely to me so now if we rerun this now we should no longer have name conflicts in our method names so yeah now we have list the comment completions find a completion update a completion delete a completion oh if it reads so nicely I love it and we don't have any name conflicts yeah that's I don't know that's pretty cool stuff the other thing we could do is work on the tests so the tests are generating using the same sort of attribute stuff I'll leave that as an exercise for the reader but one thing I don't want to leave for you as a reader is the fun of getting the URL populated here so there's another feature of Thor called option so you could say option and then whatever the option is that you want to pass in when you're defining all of the commands in a Thor class for your command line interface usually you say like the description and then you'll have a method and it'll have some documentation about that method when I was looking around the rails codebase it didn't look like that's how it worked and because we just have one command in our API client generator we can say class option and this is going to be an option that is available for all of the methods in here and in this case we'll call it URL and this is going to be a string the type of the thing is a string we're going to have a default and this will be the API base URL okay so now what we can do is we can use that option by saying option so here we can make like another shortcut method here maybe def URL and we can access that with option and then in our client. t thing here when we're generating the client now we can say URL so we'll generate and spit out the URL there so let's do the same thing- URL htps api. open.com and yes we'll overwrite it and now let's look at our open AI client and awesome it's got api. open.com Fant fantastic this is super cool so you can use a combination of these like little dashes in here to remove some of the spacing this like trims white space as part of Erb all right so let's see if we can clean up the output so that it doesn't look all garby uh and okay so we'll start with that and let's take a look at what that looks like oh okay so that added more space or something I don't know or yeah I guess it like removed some around so this is this is definitely like a trial and error type situation client TT yeah I haven't found a perfect way to do this yet like to track down where to add all these and also like it's probably when you look at these template templates or whatever the generator templates like they're usually like pretty hard to read because just to get like all of the indenting right like you want your class to come out right and it can just be a mess we're getting closer we've got to we still have some new lines that we've got to clean up but yeah we're definitely getting closer let's remove some more of these all right a lot of fiddling but I think we got it pretty close so the other thing I wanted to do was like if you pass in some arguments if you pass in some attributes then we will ignore most of the the default stuff that came with the template so if if attributes is empty then we'll render the rest of this stuff otherwise we are going to just render the ones that are being passed in and created that way if you're passing stuff in we're only creating the ones that you care about otherwise we'll still give you the kind of like examples that you can follow and what's cool about that is you can do the same thing in the tests you could imagine I think it what I ended up doing is leaving in this Mi method because that is pretty common on most apis but also it's really helpful for all these tests so if we look back in the client test for just a second for example we might want to change all of htps example.org to this URL so that now when we generate this we're going to have the right base URL in all of the tests which is cool so you could imagine following the same pattern as we did over there but yeah it was fun to dig through all the generators and also hopefully this gives you some confidence to dive into the rails code base and figure out how things work again go check out the Thor documentation very cool jumpstar Pro rails has done wonders for us in terms of speed there's a lot of really cool batteries included that are baked in there yep so go check that out the guides the rails guides for creating and customizing generators these are really good so you can say rails G generator rails generate generator and you can build your own generators that do lots of cool stuff like build templates and other things so definitely recommend taking a look at these docs which we'll link to down in the description thanks so much for watching 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