Ruby on Rails Scaffolding

Hi, I'm Jason, the Ruby teacher here at Treehouse. 0:00 In this Rails Scaffolding Workshop we're going to take a look at how scaffolding 0:04 works in a Ruby on Rails application. 0:08 Now, what scaffolding is going to do is set up a few different things for you. 0:11 Models, routes, views, and a controller. 0:15 Now we're gonna take a thorough look at how to use a scaffold 0:20 in your Rails application. 0:23 Now scaffolding is just meant to get you up and running with a resource. 0:25 Generally you'll replace all of this over time 0:30 as you build out your application's feature. 0:32 But anyway let's take a look at how scaffolding works now. 0:35 Okay, so let's take a look at how Rails scaffolding works. 0:39 Right now I am inside of a Rails application called example app. 0:44 This is a freshly generated Rails application. 0:49 There's nothing inside it. 0:53 Now, we use scaffolding to set up resources in our application. 0:56 So, let's go ahead and set that up now. 1:02 Setting up resources is kind of a fancy way of saying that it's gonna create 1:05 a model, controller, migration, templates, and some other files for us. 1:09 So, let's go ahead and pretend that we are creating a to-do list application. 1:14 So, first let me go ahead and create the databases. 1:19 There we go, that should have created all my databases. 1:26 Now, let's go ahead And, say, we're gonna generate a scaffold for 1:28 a todo_list. 1:34 And, when we are generating a scaffold, let's go ahead and 1:37 just say, our todo list has a title and that's a string. 1:40 We're not gonna get too complicated right now. 1:44 So, we do this, we generate the scaffold todo list, press enter, 1:47 and now we can see a whole bunch of things just happened. 1:52 It created a whole bunch of files, and added routes for us. 1:55 Let's go ahead and see what it did. 2:00 So, it created this migration file called create todo lists, let's go ahead and 2:03 take a look at that. 2:07 Now I'm using Sublime Text here, you can use any text editor on your system. 2:12 So here we go, it says it created a migration called CreateToDoLists, 2:19 and you'll notice it's got a string for the title attribute. 2:25 And the title attribute was what we had on 2:30 the command line when we generated the scaffold. 2:34 So it also created a model for todo list. 2:38 Let's go ahead and look at the todo list model. 2:41 So here's the todo list model, it is just an empty model. 2:48 Let's go back and see what else happened, we have a test for 2:50 it as well as a fixture. 2:55 Let's go ahead and load up the fixture and see what that looks like. 2:58 So we open up the test directory, fixtures, TodoList.yml And 3:02 this created two different fixtures for us. 3:06 Fixtures are going to be inserted into our database and 3:11 it's just some test data for us to work with. 3:14 It added a resource to our routes called to do list. 3:19 Let's go ahead and look at that. 3:23 So if we open up our config directory and open up the routes file, 3:25 we now have this line added, resources, to-do lists. 3:29 So that sets up our todo list routes for us. 3:34 Which is going to go to the todo lists controller, 3:37 which is also the next thing that was generated for us. 3:41 Let's take a look at that. 3:45 So if we open up this to do list controller we can see we 3:49 have a few different actions here. 3:52 We've also got this before filter that sets the to do list for 3:54 these particular controller actions show, edit, update and destroy. 3:59 Let's scroll down and see what that looks like. 4:04 Well, it looks we have this set TodoList method. 4:06 This sets up an instance variable, which finds a to do list by the ID parameter, 4:09 and also where set up the TodoList params itself. 4:15 This is going to be part of strong parameters. 4:21 And, it says, inside of the controller, 4:24 that we need this TodoList parameter for the parameters to be sent in. 4:26 And, we are permitting the title attribute. 4:32 So, set_todo_list is set. 4:37 Then, we can call it in the destroy method. 4:38 Update method. 4:41 Create method sets it up itself based on the TodoList params. 4:43 Edit method, all set. 4:49 To do list just creates a todo list and 4:51 show method also gets it from the set todoList method. 4:54 Now if we were building up a real TodoList controller, this would be a good start. 4:59 This wouldn't be everything that we needed because 5:03 odds are we're gonna be replacing parts of this throughout the application. 5:06 We might decide that we need more attributes inside of the todo list. 5:10 Maybe we are going to respond to more than just HTML and JSON. 5:14 Or, maybe we need to manipulate the todo list in some way, 5:20 perhaps to add the ability to add files, not really sure. 5:23 The scaffolding is just meant to be a starting point for this application. 5:27 So let's see what else it generated. 5:33 Looks like we have some views here for index, edit, show, new, and 5:35 the form template Let's go ahead and see what those look like. 5:39 So here is the index file. 5:44 We are listing the todo lists, and it goes through, and this is interesting. 5:47 It actually displays the title for us and 5:52 then links to all of these different actions. 5:55 Go back here. It's the same thing for the edit, 5:59 show, and new pages. 6:01 Let's go ahead and take a look at new though. 6:03 We just render the form same thing on the edit page. 6:05 Here is the form file. 6:09 The form template partial just specifies it's a form for the todo list. 6:12 Shows you any errors that happen if we tried saving the to do list. 6:17 And then it creates a field for the title and a submit button. 6:22 And this is all done for us. 6:27 Finally we get a controller test and a todo list helper. 6:30 The controller test, let's take a look at that. 6:35 It's down here. 6:38 Now this is going to go through. 6:41 It uses the fixtures that were set up and just asserts that all these 6:42 things are working as expected which is that things are going to require a title. 6:48 It's given a title for us and 6:55 everything is kinda just happening as we expect it to inside of a controller. 6:56 Helper is going to be empty because we 7:02 don't know what we're going to need inside of the to do list. 7:05 So helpers are going to be used for adding view logic inside of method. 7:09 So if we wanted to say something like display to do list header. 7:15 Maybe that has the title of the to do list and 7:19 its due date for some of the items on there. 7:23 We don't know. 7:26 That would be logic that we encapsulate inside of this module, but 7:27 there's nothing to do yet. 7:31 But rail sets it up for us. 7:33 And finally we have the index.json.jbuilder and 7:35 the show.json.jbuilder. 7:40 If we were creating an API we would be using these different files. 7:42 Sorry the, here's the json builder. 7:48 We would be using the json builder files to say okay, here's our todo list, 7:50 give me the ID, title, created_at and updated_at attributes. 7:56 These created_at and updated_at attributes are set inside of the migration, 8:00 that's what this timestamps method does, creates created_at and updated_at. 8:05 And then when you create or 8:10 update a record, those are automatically updated for you in Rails. 8:13 And then finally we have a CoffeeScript file generated as a JavaScript file. 8:19 And a todo_lists style sheet created as well 8:25 in these could be used inside of our application. 8:30 This is where we would put our JavaScript logic if we had something just for 8:31 the todo list controller. 8:36 And, the same thing. 8:39 If we had todo list stylesheets that just needed to be applied to todo lists. 8:40 But, let's go ahead and look at the assets here. 8:46 By default, the application in JavaScript includes everything. 8:51 So that is going to include the todo list CoffeeScript file. 8:56 You can change this if you wanted to. 8:59 Take it out of the required_tree if you wanted more 9:01 fine grain control over when these things are loaded. 9:05 If not, it's going to apply to the whole application and 9:07 not just your todo list controller. 9:10 So, that's up to you. 9:13 Same thing occurs in the style sheet. 9:13 And this scaffold CSS file is something that's generated by Rails automatically. 9:17 It just gives you some basic styling for Rails application. 9:22 It's created when you generate a scaffold if it doesn't exist already. 9:25 So we ran the scaffold. 9:30 I'm gonna clear my screen here and let's go ahead and migrate the database, okay. 9:32 And let's see what this actually did for 9:40 us now that we saw all the files that were generated. 9:41 So if we open up the Rails application right now we can see 9:48 this is the default Ruby on Rails page. 9:51 If we wanted to get to what we just created. 9:55 We would go /todo_lists and 9:58 this would be the scaffold that was generated. 10:02 So I could create a todo list and 10:06 this will tell me the todo list was successfully created. 10:11 I could view it, could edit it if I wanted to. 10:14 And I could also destroy it. 10:18 So that's a Rails scaffold. 10:23 I'm gonna go ahead and stop the server here and clear the screen. 10:25 Now let's say we wanted to generate another scaffold for todo items. 10:30 We could do the same thing, rails generate scaffold todo_item, 10:38 and we will say that has a title, which is a string, 10:44 and a due_at column, which is a date time. 10:50 And furthermore, let's go ahead and 10:55 say that these to do items belong to the to do list. 10:57 We could say that by saying that the to do item references the to do list. 11:01 We could say, to do list. 11:06 And we give it this key, references. 11:08 Now here's something neat that you can do with scaffolding. 11:12 I'm gonna use a dash and the letter P and 11:14 that's going to pretend to create the scaffold for me. 11:17 So this didn't do anything, but it said it was going to. 11:20 It was going to create a migration and it's going to create a model. 11:24 Basically everything that was created last time. 11:29 But if we look inside of the application here, 11:32 we can close these, we'll notice that we didn't 11:37 get the controller, we didn't get the models either. 11:42 So adding -p as a flag will pretend to generate this scaffold for us. 11:47 Now, I'm gonna go ahead and just generate that. 11:53 Okay. 11:57 Now, let's take a look at this references. 11:59 If you want to set up a relationship of some sort. 12:01 Here, we're using references for todo_list. 12:06 And we're indexing that database column and also giving it a foreign key. 12:10 So if we where to migrate the database right now. 12:16 Okay, we create the todo_items table, and 12:24 if we look back at the todo item model, we can say that it belongs to a to do list. 12:28 What you'll notice is that the scaffold does not tell the to do 12:36 list that it has many to do items. 12:41 So if we wanted to do any kind of different relation 12:46 we would have to add that in this migration as well. 12:49 Now in addition to being able to pretend what we wanted. 12:53 Let's go ahead and take a look at the scaffold generator help. 12:57 So if we add two dashes and the world help. 13:07 We can see we have a bunch of different options here when we are generating 13:11 the scaffold. 13:13 And this will give us more control 13:15 over the different scaffolds that are generated. 13:18 So let's say we were scaffolding the to-do items like we just did, 13:21 and we wanted to index the name. 13:25 We could say, indexed field, give it a type, and also another colon at the index. 13:28 Now as far as options go, 13:35 here's everything we can pass to a scaffold generator. 13:36 Are we generating style sheets? 13:41 This defaults to true. 13:43 Are we generating style sheets with SCSS? 13:45 The default is SCSS. 13:49 Now we could say that We want to skip asset generation entirely which 13:51 includes JavaScript by saying no assets or skip assets. 13:56 Are we scaffolding a controller? 14:02 The default is scaffold controller. 14:05 We also get active record options. 14:08 Do we want to generate migrations, timestamps, 14:10 parents which will also add indexes and references for belongs_to columns. 14:13 You'll notice that defaults to true 14:18 which is what we said on the command line before with references. 14:21 As we scroll through we can see we have all of these built in options. 14:26 So, in addition to pretend, with -p, which is what we added before, 14:33 we can also call that with two hyphens and pretend. 14:38 If we wanted to make sure that everything was completely overwritten, 14:42 we could use the force, or -f option. 14:46 We could suppress output by doing --quiet, or -q. 14:50 Then we could skip files that already exist by typing --skip, or -s. 14:55 Now we can change all of these things from the defaults as we're generating 15:05 the scaffolds. 15:08 It tells you what the defaults are in the regular general command with help. 15:10 And those are the basics of working with Scaffolding in a Rails application. 15:18