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Active Record Associations in Rails

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Rendering Associated Models in Views

3:15 with Jay McGavren

We can use all the same association methods we were using in the Rails console within controllers and views. That's going to be the key to allowing create, read, update, and delete actions on our associated models from a user's web browser. First, let's try applying that to viewing a list of the comments associated with a Post.

Back in our blog app, we can associate comments with a post in the Rails console. But users can't view a post's comments from their browser yet. Let's fix that.

We can use all the same association methods we were using in the Rails console within controllers and views. That's going to be the key to allowing create, read, update, and delete actions on our associated models from a user's web browser. First, let's try applying that to viewing a list of the comments associated with a Post.

Here's the most direct way:

<div id="comments">
  <h1>Comments</h1>
  <!-- The `comments` method returns an array-like collection, so we can call `each` on it: -->
  <% @post.comments.each do |comment| %>
    <div>
      <strong><%= comment.name %> says:</strong>
      <%= comment.content %>
    </div>
  <% end %>
</div>

Now you've got a working list of comments for each Post. This works okay for an associated model with only two attributes. But once you start working with more complex associated models, embedding their code in the view for a different model becomes unwieldy. Up next we'll look at a better way to break up your ERB code, using partials.

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    [MUSIC] 0:00
    Working with associated models in your controllers won't be much different from 0:04
    working with them in the Rails console. 0:08
    But rendering them in your views and 0:10
    representing the association in your routes might take a little more work. 0:12
    We'll cover those details and more in this stage. 0:16
    We can associate comments with a post in the Rails console, but users of our blog 0:19
    app can't view a post's comments from their browser yet, let's fix that. 0:24
    We can use all the same association methods we were using in the Rails 0:28
    console, within controllers and view as well. 0:32
    That's going to be the key to allowing create, read, update, and 0:35
    delete actions on our associated models from a user's web browser. 0:38
    First, let's try applying that to viewing a list of the comments associated with 0:42
    a post. 0:46
    So let's go into the show view for our posts. 0:48
    And on an individual post page, 0:52
    we're going to add a div that shows all the comments for that post. 0:54
    So we'll add a new div HTML element here, and we're gonna give it an ID of comments. 0:58
    We don't have any particular use for that ID right now. 1:03
    It'll just be useful for identifying this section later. 1:06
    Let's put a level 1 heading in here of Comments. 1:10
    And let's start by looping through all the comments on our post, 1:14
    which will be in the @post instance variable. 1:19
    We can access all the comments with the comments method on that post. 1:23
    And because comments returns an array-like collection, 1:27
    we can call the each method on it to process each comment in that collection. 1:31
    So we'll provide a block here, and that block will take a parameter of comment. 1:36
    Then let's add the end keyword to end our each loop. 1:46
    The contents of this loop are going to be repeated for 1:50
    each element in the comments collection, or no times if there are no comments. 1:53
    So for each comment, we're going to create a div element. 1:58
    And in that div element, we're going to include the commenter name. 2:04
    We'll put that in a strong tag so that it gets highlighted. 2:08
    And then we'll say, comment.name 2:12
    says, And close the strong tag. 2:18
    Then we'll put the actual content of the comment down here, comment.content. 2:24
    We'll save that, and let's visit our list of posts after starting 2:31
    our Rails server up, bin/rails server. 2:36
    Reload that and visit the first post, 2:41
    which is what we've been putting the comments on. 2:43
    Show that, and there's our list of comments. 2:46
    The view looped through each comment in the collection and created a div for 2:50
    each one of them. 2:54
    So now you've got a working list of comments for each post. 2:55
    This works okay for an associated model with only two attributes, 2:58
    like comments have. 3:02
    But once you start working with more complex associated models, 3:03
    this is gonna get unwieldy to embed within the post view. 3:06
    Up next we'll look at a better way to split up the ERB code using partials. 3:10

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