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diff --git a/guides/source/getting_started.textile b/guides/source/getting_started.textile index b48ebbceb2..947abd7ba0 100644 --- a/guides/source/getting_started.textile +++ b/guides/source/getting_started.textile @@ -72,7 +72,8 @@ step needed to make this example application has been left out, so you can literally follow along step by step. You can get the complete code "here":https://github.com/lifo/docrails/tree/master/guides/code/getting_started. -By following along with this guide, you'll create a Rails project called <tt>blog</tt>, a +By following along with this guide, you'll create a Rails project called ++blog+, a (very) simple weblog. Before you can start building the application, you need to make sure that you have Rails itself installed. @@ -86,7 +87,10 @@ To install Rails, use the +gem install+ command provided by RubyGems: # gem install rails </shell> -TIP. If you're working on Windows, you can quickly install Ruby and Rails with "Rails Installer":http://railsinstaller.org. +TIP. A number of tools exist to help you quickly install Ruby and Ruby +on Rails on your system. Windows users can use "Rails +Installer":http://railsinstaller.org, while Mac OS X users can use +"Rails One Click":http://railsoneclick.com. To verify that you have everything installed correctly, you should be able to run the following: @@ -108,7 +112,8 @@ $ rails new blog This will create a Rails application called Blog in a directory called blog. -TIP: You can see all of the command line options that the Rails application builder accepts by running <tt>rails new -h</tt>. +TIP: You can see all of the command line options that the Rails +application builder accepts by running +rails new -h+. After you create the blog application, switch to its folder to continue work directly in that application: @@ -116,7 +121,10 @@ After you create the blog application, switch to its folder to continue work dir $ cd blog </shell> -The +rails new blog+ command we ran above created a folder in your working directory called <tt>blog</tt>. The <tt>blog</tt> directory has a number of auto-generated files and folders that make up the structure of a Rails application. Most of the work in this tutorial will happen in the <tt>app/</tt> folder, but here's a basic rundown on the function of each of the files and folders that Rails created by default: +The +rails new blog+ command we ran above created a folder in your +working directory called +blog+. The +blog+ directory has a number of +auto-generated files and folders that make up the structure of a Rails +application. Most of the work in this tutorial will happen in the +app/+ folder, but here's a basic rundown on the function of each of the files and folders that Rails created by default: |_.File/Folder|_.Purpose| |app/|Contains the controllers, models, views, helpers, mailers and assets for your application. You'll focus on this folder for the remainder of this guide.| @@ -385,11 +393,10 @@ This action is now displaying the parameters for the post that are coming in fro h4. Creating the Post model -Rails uses models to manage database objects, so if you want to save -data to the database you'll have to create a model. In our blog -application you want to save posts, so you'll create a +Post+ model. - -You can create a model with the following command: +Models in Rails use a singular name, and their corresponding database tables use +a plural name. Rails provides a generator for creating models, which +most Rails developers tend to use when creating new models. +To create the new model, run this command in your terminal: <shell> $ rails generate model Post title:string text:text @@ -397,7 +404,10 @@ $ rails generate model Post title:string text:text With that command we told Rails that we want a +Post+ model, which in turn should have a title attribute of type string, and a text attribute -of type text. Rails in turn responded by creating a bunch of files. For +of type text. Those attributes are automatically added to the +posts+ +table in the database and mapped to the +Post+ model. + +Rails in turn responded by creating a bunch of files. For now, we're only interested in +app/models/post.rb+ and +db/migrate/20120419084633_create_posts.rb+. The latter is responsible for creating the database structure, which is what we'll look at next. @@ -457,7 +467,7 @@ NOTE. Because you're working in the development environment by default, this command will apply to the database defined in the +development+ section of your +config/database.yml+ file. If you would like to execute migrations in another environment, for instance in production, you must explicitly pass it when -invoking the command: <tt>rake db:migrate RAILS_ENV=production</tt>. +invoking the command: +rake db:migrate RAILS_ENV=production+. h4. Saving data in the controller @@ -1095,424 +1105,65 @@ posts. In the next section will see how Rails can aid us when creating REST applications, and how we can refactor our Blog app to take advantage of it. -h4. Using the Console - -To see your validations in action, you can use the console. The console is a -command-line tool that lets you execute Ruby code in the context of your -application: - -<shell> -$ rails console -</shell> - -TIP: The default console will make changes to your database. You can instead -open a console that will roll back any changes you make by using <tt>rails console ---sandbox</tt>. - -After the console loads, you can use it to work with your application's models: - -<shell> ->> p = Post.new(:content => "A new post") -=> #<Post id: nil, name: nil, title: nil, - content: "A new post", created_at: nil, - updated_at: nil> ->> p.save -=> false ->> p.errors.full_messages -=> ["Name can't be blank", "Title can't be blank", "Title is too short (minimum is 5 characters)"] -</shell> +h4. Going Deeper into REST -This code shows creating a new +Post+ instance, attempting to save it and -getting +false+ for a return value (indicating that the save failed), and -inspecting the +errors+ of the post. - -When you're finished, type +exit+ and hit +return+ to exit the console. - -TIP: Unlike the development web server, the console does not automatically load -your code afresh for each line. If you make changes to your models (in your editor) -while the console is open, type +reload!+ at the console prompt to load them. - -h4. Listing All Posts - -Let's dive into the Rails code a little deeper to see how the application is -showing us the list of Posts. Open the file -+app/controllers/posts_controller.rb+ and look at the -+index+ action: +We've now covered all the CRUD actions of a REST app. We did so by +declaring separate routes with the appropriate verbs into ++config/routes.rb+. Here's how that file looks so far: <ruby> -def index - @posts = Post.all - - respond_to do |format| - format.html # index.html.erb - format.json { render :json => @posts } - end -end -</ruby> - -+Post.all+ returns all of the posts currently in the database as an array -of +Post+ records that we store in an instance variable called +@posts+. - -TIP: For more information on finding records with Active Record, see "Active -Record Query Interface":active_record_querying.html. - -The +respond_to+ block handles both HTML and JSON calls to this action. If you -browse to "http://localhost:3000/posts.json":http://localhost:3000/posts.json, -you'll see a JSON containing all of the posts. The HTML format looks for a view -in +app/views/posts/+ with a name that corresponds to the action name. Rails -makes all of the instance variables from the action available to the view. -Here's +app/views/posts/index.html.erb+: - -<erb> -<h1>Listing posts</h1> - -<table> - <tr> - <th>Name</th> - <th>Title</th> - <th>Content</th> - <th></th> - <th></th> - <th></th> - </tr> - -<% @posts.each do |post| %> - <tr> - <td><%= post.name %></td> - <td><%= post.title %></td> - <td><%= post.content %></td> - <td><%= link_to 'Show', post %></td> - <td><%= link_to 'Edit', edit_post_path(post) %></td> - <td><%= link_to 'Destroy', post, :confirm => 'Are you sure?', - :method => :delete %></td> - </tr> -<% end %> -</table> - -<br /> - -<%= link_to 'New post', new_post_path %> -</erb> - -This view iterates over the contents of the +@posts+ array to display content -and links. A few things to note in the view: - -* +link_to+ builds a hyperlink to a particular destination -* +edit_post_path+ and +new_post_path+ are helpers that Rails provides as part of RESTful routing. You'll see a variety of these helpers for the different actions that the controller includes. - -NOTE. In previous versions of Rails, you had to use +<%=h post.name %>+ so -that any HTML would be escaped before being inserted into the page. In Rails -3 and above, this is now the default. To get unescaped HTML, you now use <tt><%= raw post.name %></tt>. - -TIP: For more details on the rendering process, see "Layouts and Rendering in -Rails":layouts_and_rendering.html. - -h4. Customizing the Layout - -The view is only part of the story of how HTML is displayed in your web browser. -Rails also has the concept of +layouts+, which are containers for views. When -Rails renders a view to the browser, it does so by putting the view's HTML into -a layout's HTML. In previous versions of Rails, the +rails generate scaffold+ -command would automatically create a controller specific layout, like -+app/views/layouts/posts.html.erb+, for the posts controller. However this has -been changed in Rails 3. An application specific +layout+ is used for all the -controllers and can be found in +app/views/layouts/application.html.erb+. Open -this layout in your editor and modify the +body+ tag to include the style directive -below: - -<erb> -<!DOCTYPE html> -<html> -<head> - <title>Blog</title> - <%= stylesheet_link_tag "application" %> - <%= javascript_include_tag "application" %> - <%= csrf_meta_tags %> -</head> -<body style="background-color: #EEEEEE;"> - -<%= yield %> - -</body> -</html> -</erb> - -Now when you refresh the +/posts+ page, you'll see a gray background to the -page. This same gray background will be used throughout all the views. - -h4. Creating New Posts - -Creating a new post involves two actions. The first is the +new+ action, which -instantiates an empty +Post+ object: - -<ruby> -def new - @post = Post.new - - respond_to do |format| - format.html # new.html.erb - format.json { render :json => @post } - end -end -</ruby> - -The +new.html.erb+ view displays this empty Post to the user: - -<erb> -<h1>New post</h1> - -<%= render 'form' %> - -<%= link_to 'Back', posts_path %> -</erb> - -The +<%= render 'form' %>+ line is our first introduction to _partials_ in -Rails. A partial is a snippet of HTML and Ruby code that can be reused in -multiple locations. In this case, the form used to make a new post is basically -identical to the form used to edit a post, both having text fields for the name and -title, a text area for the content, and a button to create the new post or to update -the existing one. - -If you take a look at +views/posts/_form.html.erb+ file, you will see the -following: - -<erb> -<%= form_for(@post) do |f| %> - <% if @post.errors.any? %> - <div id="errorExplanation"> - <h2><%= pluralize(@post.errors.count, "error") %> prohibited - this post from being saved:</h2> - <ul> - <% @post.errors.full_messages.each do |msg| %> - <li><%= msg %></li> - <% end %> - </ul> - </div> - <% end %> - - <div class="field"> - <%= f.label :name %><br /> - <%= f.text_field :name %> - </div> - <div class="field"> - <%= f.label :title %><br /> - <%= f.text_field :title %> - </div> - <div class="field"> - <%= f.label :content %><br /> - <%= f.text_area :content %> - </div> - <div class="actions"> - <%= f.submit %> - </div> -<% end %> -</erb> - -This partial receives all the instance variables defined in the calling view -file. In this case, the controller assigned the new +Post+ object to +@post+, -which will thus be available in both the view and the partial as +@post+. - -For more information on partials, refer to the "Layouts and Rendering in -Rails":layouts_and_rendering.html#using-partials guide. - -The +form_for+ block is used to create an HTML form. Within this block, you have -access to methods to build various controls on the form. For example, -+f.text_field :name+ tells Rails to create a text input on the form and to hook -it up to the +name+ attribute of the instance being displayed. You can only use -these methods with attributes of the model that the form is based on (in this -case +name+, +title+, and +content+). Rails uses +form_for+ in preference to -having you write raw HTML because the code is more succinct, and because it -explicitly ties the form to a particular model instance. - -The +form_for+ block is also smart enough to work out if you are doing a _New -Post_ or an _Edit Post_ action, and will set the form +action+ tags and submit -button names appropriately in the HTML output. - -TIP: If you need to create an HTML form that displays arbitrary fields, not tied -to a model, you should use the +form_tag+ method, which provides shortcuts for -building forms that are not necessarily tied to a model instance. - -When the user clicks the +Create Post+ button on this form, the browser will -send information back to the +create+ action of the controller (Rails knows to -call the +create+ action because the form is sent with an HTTP POST request; -that's one of the conventions that were mentioned earlier): - -<ruby> -def create - @post = Post.new(params[:post]) - - respond_to do |format| - if @post.save - format.html { redirect_to(@post, - :notice => 'Post was successfully created.') } - format.json { render :json => @post, - :status => :created, :location => @post } - else - format.html { render :action => "new" } - format.json { render :json => @post.errors, - :status => :unprocessable_entity } - end - end -end -</ruby> - -The +create+ action instantiates a new Post object from the data supplied by the -user on the form, which Rails makes available in the +params+ hash. After -successfully saving the new post, +create+ returns the appropriate format that -the user has requested (HTML in our case). It then redirects the user to the -resulting post +show+ action and sets a notice to the user that the Post was -successfully created. - -If the post was not successfully saved, due to a validation error, then the -controller returns the user back to the +new+ action with any error messages so -that the user has the chance to fix the error and try again. - -The "Post was successfully created." message is stored in the Rails -+flash+ hash (usually just called _the flash_), so that messages can be carried -over to another action, providing the user with useful information on the status -of their request. In the case of +create+, the user never actually sees any page -rendered during the post creation process, because it immediately redirects to -the new +Post+ as soon as Rails saves the record. The Flash carries over a message to -the next action, so that when the user is redirected back to the +show+ action, -they are presented with a message saying "Post was successfully created." - -h4. Showing an Individual Post - -When you click the +show+ link for a post on the index page, it will bring you -to a URL like +http://localhost:3000/posts/1+. Rails interprets this as a call -to the +show+ action for the resource, and passes in +1+ as the +:id+ parameter. -Here's the +show+ action: - -<ruby> -def show - @post = Post.find(params[:id]) - - respond_to do |format| - format.html # show.html.erb - format.json { render :json => @post } - end -end +get "posts" => "posts#index" +get "posts/new" +post "posts/create" +get "posts/:id" => "posts#show", :as => :post +get "posts/:id/edit" => "posts#edit" +put "posts/:id" => "posts#update" +delete "posts/:id" => "posts#destroy" </ruby> -The +show+ action uses +Post.find+ to search for a single record in the database -by its id value. After finding the record, Rails displays it by using -+app/views/posts/show.html.erb+: - -<erb> -<p id="notice"><%= notice %></p> - -<p> - <b>Name:</b> - <%= @post.name %> -</p> - -<p> - <b>Title:</b> - <%= @post.title %> -</p> - -<p> - <b>Content:</b> - <%= @post.content %> -</p> - - -<%= link_to 'Edit', edit_post_path(@post) %> | -<%= link_to 'Back', posts_path %> -</erb> - -h4. Editing Posts - -Like creating a new post, editing a post is a two-part process. The first step -is a request to +edit_post_path(@post)+ with a particular post. This calls the -+edit+ action in the controller: +That's a lot to type for covering a single *resource*. Fortunately, +Rails provides a +resources+ method which can be used to declare a +standard REST resource. Here's how +config/routes/rb+ looks after the +cleanup: <ruby> -def edit - @post = Post.find(params[:id]) -end -</ruby> - -After finding the requested post, Rails uses the +edit.html.erb+ view to display -it: - -<erb> -<h1>Editing post</h1> - -<%= render 'form' %> - -<%= link_to 'Show', @post %> | -<%= link_to 'Back', posts_path %> -</erb> - -Again, as with the +new+ action, the +edit+ action is using the +form+ partial. -This time, however, the form will do a PUT action to the +PostsController+ and the -submit button will display "Update Post". - -Submitting the form created by this view will invoke the +update+ action within -the controller: +Blog::Application.routes.draw do -<ruby> -def update - @post = Post.find(params[:id]) + resources :posts - respond_to do |format| - if @post.update_attributes(params[:post]) - format.html { redirect_to(@post, - :notice => 'Post was successfully updated.') } - format.json { head :no_content } - else - format.html { render :action => "edit" } - format.json { render :json => @post.errors, - :status => :unprocessable_entity } - end - end + root :to => "welcome#index" end </ruby> -In the +update+ action, Rails first uses the +:id+ parameter passed back from -the edit view to locate the database record that's being edited. The -+update_attributes+ call then takes the +post+ parameter (a hash) from the request -and applies it to this record. If all goes well, the user is redirected to the -post's +show+ action. If there are any problems, it redirects back to the +edit+ action to -correct them. - -h4. Destroying a Post - -Finally, clicking one of the +destroy+ links sends the associated id to the -+destroy+ action: - -<ruby> -def destroy - @post = Post.find(params[:id]) - @post.destroy +If you run +rake routes+, you'll see that all the routes that we +declared before are still available, and the app still works as before. - respond_to do |format| - format.html { redirect_to posts_url } - format.json { head :no_content } - end -end -</ruby> +<shell> +# rake routes + posts GET /posts(.:format) posts#index + POST /posts(.:format) posts#create + new_post GET /posts/new(.:format) posts#new +edit_post GET /posts/:id/edit(.:format) posts#edit + post GET /posts/:id(.:format) posts#show + PUT /posts/:id(.:format) posts#update + DELETE /posts/:id(.:format) posts#destroy + root / welcome#index +</shell> -The +destroy+ method of an Active Record model instance removes the -corresponding record from the database. After that's done, there isn't any -record to display, so Rails redirects the user's browser to the index action of -the controller. +TIP: In general, Rails encourages the use of resources objects in place +of declaring routes manually. For more information about routing, see +"Rails Routing from the Outside In":routing.html. h3. Adding a Second Model -Now that you've seen what a model built with scaffolding looks like, it's time to -add a second model to the application. The second model will handle comments on +It's time to add a second model to the application. The second model will handle comments on blog posts. h4. Generating a Model -Models in Rails use a singular name, and their corresponding database tables use -a plural name. For the model to hold comments, the convention is to use the name -+Comment+. Even if you don't want to use the entire apparatus set up by -scaffolding, most Rails developers still use generators to make things like -models and controllers. To create the new model, run this command in your -terminal: +We're going to se the same generator that we used before when creating +the +Post+ model. This time we'll create a +Comment+ model to hold +reference of post comments. Run this command in your terminal: <shell> $ rails generate model Comment commenter:string body:text post:references @@ -1600,7 +1251,6 @@ You'll need to edit the +post.rb+ file to add the other side of the association: <ruby> class Post < ActiveRecord::Base - validates :name, :presence => true validates :title, :presence => true, :length => { :minimum => 5 } @@ -1619,9 +1269,7 @@ h4. Adding a Route for Comments As with the +welcome+ controller, we will need to add a route so that Rails knows where we would like to navigate to see +comments+. Open up the -+config/routes.rb+ file again. Near the top, you will see the entry for +posts+ -that was added automatically by the scaffold generator: <tt>resources -:posts</tt>. Edit it as follows: ++config/routes.rb+ file again, and edit it as follows: <ruby> resources :posts do @@ -1639,7 +1287,7 @@ In":routing.html guide. h4. Generating a Controller With the model in hand, you can turn your attention to creating a matching -controller. Again, there's a generator for this: +controller. Again, we'll use the same generator we used before: <shell> $ rails generate controller Comments @@ -1666,40 +1314,33 @@ So first, we'll wire up the Post show template (+/app/views/posts/show.html.erb+) to let us make a new comment: <erb> -<p id="notice"><%= notice %></p> - -<p> - <b>Name:</b> - <%= @post.name %> -</p> - <p> - <b>Title:</b> + <strong>Title:</strong> <%= @post.title %> </p> <p> - <b>Content:</b> - <%= @post.content %> + <strong>Text:</strong> + <%= @post.texthttp://beginningruby.org/ %> </p> <h2>Add a comment:</h2> <%= form_for([@post, @post.comments.build]) do |f| %> - <div class="field"> + <p> <%= f.label :commenter %><br /> <%= f.text_field :commenter %> - </div> - <div class="field"> + </p> + <p> <%= f.label :body %><br /> <%= f.text_area :body %> - </div> - <div class="actions"> + </p> + <p> <%= f.submit %> - </div> + </p> <% end %> <%= link_to 'Edit Post', edit_post_path(@post) %> | -<%= link_to 'Back to Posts', posts_path %> | +<%= link_to 'Back to Posts', posts_path %> </erb> This adds a form on the +Post+ show page that creates a new comment by @@ -1732,60 +1373,53 @@ template. This is where we want the comment to show, so let's add that to the +app/views/posts/show.html.erb+. <erb> -<p id="notice"><%= notice %></p> - <p> - <b>Name:</b> - <%= @post.name %> -</p> - -<p> - <b>Title:</b> + <strong>Title:</strong> <%= @post.title %> </p> <p> - <b>Content:</b> - <%= @post.content %> + <strong>Text:</strong> + <%= @post.texthttp://beginningruby.org/ %> </p> <h2>Comments</h2> <% @post.comments.each do |comment| %> <p> - <b>Commenter:</b> + <strong>Commenter:</strong> <%= comment.commenter %> </p> <p> - <b>Comment:</b> + <strong>Comment:</strong> <%= comment.body %> </p> <% end %> <h2>Add a comment:</h2> <%= form_for([@post, @post.comments.build]) do |f| %> - <div class="field"> + <p> <%= f.label :commenter %><br /> <%= f.text_field :commenter %> - </div> - <div class="field"> + </p> + <p> <%= f.label :body %><br /> <%= f.text_area :body %> - </div> - <div class="actions"> + </p> + <p> <%= f.submit %> - </div> + </p> <% end %> -<br /> - <%= link_to 'Edit Post', edit_post_path(@post) %> | -<%= link_to 'Back to Posts', posts_path %> | +<%= link_to 'Back to Posts', posts_path %> </erb> Now you can add posts and comments to your blog and have them show up in the right places. +!images/getting_started/post_with_comments.png(Post with Comments)! + h3. Refactoring Now that we have posts and comments working, take a look at the @@ -1800,12 +1434,12 @@ following into it: <erb> <p> - <b>Commenter:</b> + <strong>Commenter:</strong> <%= comment.commenter %> </p> <p> - <b>Comment:</b> + <strong>Comment:</strong> <%= comment.body %> </p> </erb> @@ -1814,21 +1448,14 @@ Then you can change +app/views/posts/show.html.erb+ to look like the following: <erb> -<p id="notice"><%= notice %></p> - <p> - <b>Name:</b> - <%= @post.name %> -</p> - -<p> - <b>Title:</b> + <strong>Title:</strong> <%= @post.title %> </p> <p> - <b>Content:</b> - <%= @post.content %> + <strong>Text:</strong> + <%= @post.texthttp://beginningruby.org/ %> </p> <h2>Comments</h2> @@ -1836,23 +1463,21 @@ following: <h2>Add a comment:</h2> <%= form_for([@post, @post.comments.build]) do |f| %> - <div class="field"> + <p> <%= f.label :commenter %><br /> <%= f.text_field :commenter %> - </div> - <div class="field"> + </p> + <p> <%= f.label :body %><br /> <%= f.text_area :body %> - </div> - <div class="actions"> + </p> + <p> <%= f.submit %> - </div> + </p> <% end %> -<br /> - <%= link_to 'Edit Post', edit_post_path(@post) %> | -<%= link_to 'Back to Posts', posts_path %> | +<%= link_to 'Back to Posts', posts_path %> </erb> This will now render the partial in +app/views/comments/_comment.html.erb+ once @@ -1868,50 +1493,38 @@ create a file +app/views/comments/_form.html.erb+ containing: <erb> <%= form_for([@post, @post.comments.build]) do |f| %> - <div class="field"> + <p> <%= f.label :commenter %><br /> <%= f.text_field :commenter %> - </div> - <div class="field"> + </p> + <p> <%= f.label :body %><br /> <%= f.text_area :body %> - </div> - <div class="actions"> + </p> + <p> <%= f.submit %> - </div> + </p> <% end %> </erb> Then you make the +app/views/posts/show.html.erb+ look like the following: <erb> -<p id="notice"><%= notice %></p> - <p> - <b>Name:</b> - <%= @post.name %> -</p> - -<p> - <b>Title:</b> + <strong>Title:</strong> <%= @post.title %> </p> <p> - <b>Content:</b> - <%= @post.content %> + <strong>Text:</strong> + <%= @post.texthttp://beginningruby.org/ %> </p> -<h2>Comments</h2> -<%= render @post.comments %> - <h2>Add a comment:</h2> <%= render "comments/form" %> -<br /> - <%= link_to 'Edit Post', edit_post_path(@post) %> | -<%= link_to 'Back to Posts', posts_path %> | +<%= link_to 'Back to Posts', posts_path %> </erb> The second render just defines the partial template we want to render, @@ -1933,12 +1546,12 @@ So first, let's add the delete link in the <erb> <p> - <b>Commenter:</b> + <strong>Commenter:</strong> <%= comment.commenter %> </p> <p> - <b>Comment:</b> + <strong>Comment:</strong> <%= comment.body %> </p> @@ -1987,7 +1600,6 @@ model, +app/models/post.rb+, as follows: <ruby> class Post < ActiveRecord::Base - validates :name, :presence => true validates :title, :presence => true, :length => { :minimum => 5 } has_many :comments, :dependent => :destroy @@ -2016,11 +1628,8 @@ class PostsController < ApplicationController http_basic_authenticate_with :name => "dhh", :password => "secret", :except => [:index, :show] - # GET /posts - # GET /posts.json def index @posts = Post.all - respond_to do |format| # snipped for brevity </ruby> @@ -2042,213 +1651,6 @@ Authentication challenge !images/challenge.png(Basic HTTP Authentication Challenge)! -h3. Building a Multi-Model Form - -Another feature of your average blog is the ability to tag posts. To implement -this feature your application needs to interact with more than one model on a -single form. Rails offers support for nested forms. - -To demonstrate this, we will add support for giving each post multiple tags, -right in the form where you create the post. First, create a new model to hold -the tags: - -<shell> -$ rails generate model Tag name:string post:references -</shell> - -Again, run the migration to create the database table: - -<shell> -$ rake db:migrate -</shell> - -Next, edit the +post.rb+ file to create the other side of the association, and -to tell Rails (via the +accepts_nested_attributes_for+ macro) that you intend to -edit tags via posts: - -<ruby> -class Post < ActiveRecord::Base - validates :name, :presence => true - validates :title, :presence => true, - :length => { :minimum => 5 } - - has_many :comments, :dependent => :destroy - has_many :tags - - accepts_nested_attributes_for :tags, :allow_destroy => :true, - :reject_if => proc { |attrs| attrs.all? { |k, v| v.blank? } } -end -</ruby> - -The +:allow_destroy+ option tells Rails to enable destroying tags through the -nested attributes (you'll handle that by displaying a "remove" checkbox on the -view that you'll build shortly). The +:reject_if+ option prevents saving new -tags that do not have any attributes filled in. - -We will modify +views/posts/_form.html.erb+ to render a partial to make a tag: - -<erb> -<% @post.tags.build %> -<%= form_for(@post) do |post_form| %> - <% if @post.errors.any? %> - <div id="errorExplanation"> - <h2><%= pluralize(@post.errors.count, "error") %> prohibited this post from being saved:</h2> - <ul> - <% @post.errors.full_messages.each do |msg| %> - <li><%= msg %></li> - <% end %> - </ul> - </div> - <% end %> - - <div class="field"> - <%= post_form.label :name %><br /> - <%= post_form.text_field :name %> - </div> - <div class="field"> - <%= post_form.label :title %><br /> - <%= post_form.text_field :title %> - </div> - <div class="field"> - <%= post_form.label :content %><br /> - <%= post_form.text_area :content %> - </div> - <h2>Tags</h2> - <%= render :partial => 'tags/form', - :locals => {:form => post_form} %> - <div class="actions"> - <%= post_form.submit %> - </div> -<% end %> -</erb> - -Note that we have changed the +f+ in +form_for(@post) do |f|+ to +post_form+ to -make it easier to understand what is going on. - -This example shows another option of the render helper, being able to pass in -local variables, in this case, we want the local variable +form+ in the partial -to refer to the +post_form+ object. - -We also add a <tt>@post.tags.build</tt> at the top of this form. This is to make -sure there is a new tag ready to have its name filled in by the user. If you do -not build the new tag, then the form will not appear as there is no new Tag -object ready to create. - -Now create the folder <tt>app/views/tags</tt> and make a file in there called -<tt>_form.html.erb</tt> which contains the form for the tag: - -<erb> -<%= form.fields_for :tags do |tag_form| %> - <div class="field"> - <%= tag_form.label :name, 'Tag:' %> - <%= tag_form.text_field :name %> - </div> - <% unless tag_form.object.nil? || tag_form.object.new_record? %> - <div class="field"> - <%= tag_form.label :_destroy, 'Remove:' %> - <%= tag_form.check_box :_destroy %> - </div> - <% end %> -<% end %> -</erb> - -Finally, we will edit the <tt>app/views/posts/show.html.erb</tt> template to -show our tags. - -<erb> -<p id="notice"><%= notice %></p> - -<p> - <b>Name:</b> - <%= @post.name %> -</p> - -<p> - <b>Title:</b> - <%= @post.title %> -</p> - -<p> - <b>Content:</b> - <%= @post.content %> -</p> - -<p> - <b>Tags:</b> - <%= @post.tags.map { |t| t.name }.join(", ") %> -</p> - -<h2>Comments</h2> -<%= render @post.comments %> - -<h2>Add a comment:</h2> -<%= render "comments/form" %> - - -<%= link_to 'Edit Post', edit_post_path(@post) %> | -<%= link_to 'Back to Posts', posts_path %> | -</erb> - -With these changes in place, you'll find that you can edit a post and its tags -directly on the same view. - -However, that method call <tt>@post.tags.map { |t| t.name }.join(", ")</tt> is -awkward, we could handle this by making a helper method. - -h3. View Helpers - -View Helpers live in <tt>app/helpers</tt> and provide small snippets of reusable -code for views. In our case, we want a method that strings a bunch of objects -together using their name attribute and joining them with a comma. As this is -for the Post show template, we put it in the PostsHelper. - -Open up <tt>app/helpers/posts_helper.rb</tt> and add the following: - -<erb> -module PostsHelper - def join_tags(post) - post.tags.map { |t| t.name }.join(", ") - end -end -</erb> - -Now you can edit the view in <tt>app/views/posts/show.html.erb</tt> to look like -this: - -<erb> -<p id="notice"><%= notice %></p> - -<p> - <b>Name:</b> - <%= @post.name %> -</p> - -<p> - <b>Title:</b> - <%= @post.title %> -</p> - -<p> - <b>Content:</b> - <%= @post.content %> -</p> - -<p> - <b>Tags:</b> - <%= join_tags(@post) %> -</p> - -<h2>Comments</h2> -<%= render @post.comments %> - -<h2>Add a comment:</h2> -<%= render "comments/form" %> - - -<%= link_to 'Edit Post', edit_post_path(@post) %> | -<%= link_to 'Back to Posts', posts_path %> | -</erb> - h3. What's Next? Now that you've seen your first Rails application, you should feel free to |