Updating an Associated Record

6:40 with Jay McGavren

We've added a way to create comments that belong to a post. Now let's add a means of updating those comments.

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We've added a way to create comments that belong to a post. Now let's add a means of updating those comments.

We want an "edit" link to appear next to each comment.
We'll get that by editing the _comment partial.

views/comments/_comment.html.erb

<div class="comment-admin">
  <%= link_to "Edit", edit_post_comment_path(@post, comment) %>
</div>

Next we need an edit action on the CommentsController:

controllers/comments_controller.rb

  def edit
    @post = Post.find(params[:post_id])
    @comment = Comment.find(params[:id])
  end

@post = Post.find(params[:post_id]) code is repeated between create and edit actions, and we'll need @post for other actions
Use before_action to set @post

class CommentsController < ApplicationController
  before_action :set_post
  def create
    @comment = @post.comments.create(comment_params)
    redirect_to @post
  end
  def edit
    @comment = Comment.find(params[:id])
  end
  private
  def comment_params
    params.require(:comment).permit(:name, :content)
  end
  def set_post
    @post = Post.find(params[:post_id])
  end
end

When we click the "Edit" link, it calls our edit action, but there's no view. So let's create one:

views/comments/edit.html.erb

<h1>Edit Comment</h1>
<%= render partial: "form", locals: {comment: @comment} %>

We need an update action on CommentsController so we can submit the form:

  def update
    @comment = Comment.find(params[:id])
    @comment.update(comment_params)
    redirect_to @post # @post will be set by before_action
  end

0:00
We've added a way to create comments that belong to a post.
0:03
Now let's add a means of updating those comments.
0:06
We're going to want an edit link to appear next to each comment in the list.
0:10
We'll get that by editing the comment partial.
0:13
So we'll go here to our views directory > comments sub-directory, and
0:17
we'll edit the comment partial.
0:19
Here within the main comment div we're going to add a new div, and
0:24
we'll give it a class of comment admin.
0:28
Should be useful later, we're not going to use it right now.
0:33
Close out the div.
0:36
And now to set up our link.
0:37
We'll insert an erb tag, with a call to the link_to method.
0:43
We're going to want the link text to read Edit, as in edit the current comment.
0:48
And now we need to provide the path that the link is going to point to.
0:51
We're going to call edit_post_comment_path.
0:58
And this call is going to need multiple parameters.
1:01
First, it's going to need a post to provide the ID used in the post ID URL
1:05
parameter.
1:06
So we'll get that by providing the post object that's in the post instance
1:10
variable.
1:12
Then it's going to need a common ID that it's going to edit.
1:15
You can get that by providing the common metal object that's in the common
1:20
local variable.
1:23
Close out the erb tag and save that, and
1:26
let's refresh our browser and there are our edit links.
1:31
But if we click on it,
1:32
we'll see the action edit could not be found on the CommentsController.
1:37
So we're gonna need to go to our comment controller and add that action.
1:45
So we'll define and edit method.
1:51
And again, we're going to need the post that the comment belongs to.
1:54
So we'll assign to the post instance variable
1:59
the result of calling Post.find with the parameter
2:05
post_id, which it'll get from the URL.
2:11
Then we're also going to need the comment that we're working with,
2:14
which will assign to the comment instance variable.
2:17
And that will be the result, we'll call it comment.find with the ID parameter.
2:25
Let's save this and try reloading.
2:30
Visit the edit link again.
2:33
And it looks like it's getting to the edit action successfully.
2:36
We don't have a view to render for this action right now,
2:38
but we'll take care of that momentarily.
2:41
There's another issue I want to address first.
2:44
Notice that this post = Post.find(params[post_id]) code is
2:48
repeated between both the create and edit methods.
2:52
And we're going to need our post instance variable set for other actions, too.
2:56
Let's go ahead and cut this code out of there and
3:00
add a private method named set post.
3:06
Paste in there.
3:11
Then we can remove that code from our edit method as well.
3:17
And we can set set_post up to be called as a before_action on the controller.
3:29
Now before both our create and edit actions run this set_post method will
3:34
be called and the post instance variable will be set.
3:40
Let's save that now let's get back to our original problem.
3:43
Only click on the edit link, it calls our edit action but
3:47
there's no view for it to render.
3:50
So let's go and create that now.
3:52
We'll go into the views comments controller and
3:56
we're going to create a new file, named edit.html.erb.
4:01
We'll add a heading saying what we're doing on this page.
4:03
We're editing a comment.
4:08
And because we already have our form partial,
4:10
all we have to do is call render with that partial.
4:14
So we'll say render partial form and
4:19
all we have to do is say form.
4:22
We don't have to specify what directory it's contained.
4:26
Since it's in the same directory as this edit few.
4:29
And then we need to set up the comment local variable.
4:32
So we'll say Locals Comment and we're going to set
4:38
that equal to our comments instance variable.
4:42
Save that and let's go back to our post view and
4:47
try editing a comment again.
4:51
And this time the edit template is called which in turn calls the form partial.
4:56
So let's make a little change to this, we will add a little more emphasis on
5:00
the comment content, and now let's try submitting the form.
5:04
We get the error that there's no update action on our comments controller, so
5:08
let's add that now.
5:13
We'll add a method named update.
5:18
And first, we're going to need to find the comment that we're working with.
5:21
So we'll assign to the comment instance variable
5:27
the result of calling Comment.find the id parameter.
5:37
Then we need to update this comment with our comment parameters.
5:40
So we'll say comment.update comment_params.
5:48
And as it does when we're creating a new comment, it'll call the comment params
5:53
method and use those parameters to update our existing comment object.
5:57
Finally, we're going to need to show our updated comment object,
6:01
which we're going to want to do in the context of a post.
6:03
So we'll say redirect_to @post.
6:10
Remember that we set up the set_post before action, so
6:14
that's this @post instance variable.
6:16
Save that, and let's try editing that comment again.
6:22
Go here, we'll add a little more emphasis and we'll hit Update Comment and
6:27
you can see our edited comment here in the list on the post page.
6:32
So now we've got updating of a comment working as well.
6:35
The last thing we'll need is the ability to delete comments from a post.
6:39
We'll look at that next.

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Active Record Associations in Rails

Updating an Associated Record

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