Creating an Associated Record

So, far we've only been able to create comments via the Rails console. 0:00 It's finally time to set up the creation of comments via the browser. 0:03 This is going to work a lot like the creation of stand-alone models like 0:08 posts and pages that we saw in previous courses. 0:11 The difference is that each comment will be created in the context of the post it 0:14 belongs to. 0:18 The form to add a comment will be on a post show page. 0:19 And we'll need a post ID to use when saving the comment model object to 0:23 the database. 0:26 So let's go to the show view for posts, and we're going to add a form for 0:28 adding a comment that belongs to this post. 0:32 So first, we're going to create a new header and we'll say Add a Comment. 0:35 And then we're going to render the form from a partial. 0:42 So we'll insert an ERB tag with a call to render. 0:45 And we're going to specify a partial render that'll be in the comments folder. 0:50 And it's going to be a partial named form. 0:57 Again no underscore needed in the name when you're calling render. 1:00 Then we are going to add the locals argument to render, 1:04 and we are going to specify that the comment variable 1:06 should be set to posts.comments.new. 1:11 This is the series of methods that you call when you want to create a new comment 1:16 that belongs to a particular post. 1:21 Close out the ERB tag and save our work. 1:25 Then here in the views, comments directory, we're going to 1:29 create another file, and this one is going to be named _form.html.erb. 1:34 We're going to insert an ERB tag with a call to 1:41 form_for, And now this part is interesting. 1:45 The path that we submit the form to is going to need include a post ID. 1:50 So we'll provide that by providing an array here, it'll be a two element array. 1:54 And the first element is going to be the resource that 2:00 our comment is nested within. 2:03 So that'll be post, form_for will derive the post ID from this post object. 2:05 The second element of the array will be the model object that's nested 2:11 within the outer resource. 2:15 So that'll be the contents of our comment variable. 2:17 The form_for method takes a block so we'll provide a block here. 2:21 We'll take the form object as a parameter to that block. 2:25 And then down here, we're going to need the end keyword to end the form_for block. 2:31 Now for the actual HTML contents of that form. 2:37 We'll set up div here for our first field, 2:42 which is going to be the comment submitter's name. 2:44 We'll give that a class of field. 2:48 Close the div. 2:53 And then we're going to need to call methods on the form object to set up 2:57 a label for this field, and the actual field itself. 3:01 So we'll insert an ERB tag with a call to f.label. 3:05 That's going to be for the main field. 3:09 And then another ERB tag with a call to f.text_field. 3:13 That'll also be for the name field. 3:20 Then we'll need another field for the comment content. 3:24 I'm just going to copy paste this first div since the code will be very similar 3:26 for the two. 3:30 But instead of working with the name attribute, 3:32 we're going to be working with the comment content attribute. 3:35 Now labeling this as content isn't going to mean much for our users. 3:39 So I'm going to add an extra argument here to make sure that 3:42 we use the text comment when labeling this content field. 3:47 Then instead of a call to text_field, which produces just a one line field, 3:52 we're going to say text_area so that the user can enter several lines of text. 3:57 And this will be also for the content attribute. 4:02 Finally, we're going to need a button for submitting the form. 4:09 So we'll add another a div down here that's gonna have a class of actions. 4:12 Oops, little typo there. 4:21 Div, close the div out. 4:22 And in that div we're going to put a form submit button, f.submit. 4:26 Save that and let's try going to our browser. 4:33 First, let's exit out of the rails console here, and run our rails server. 4:37 Okay, now let's reload our post show page. 4:44 Whoops it looks like I made a typo in my instance variable name. 4:48 Let's go back to our show view and the instance variable isn't posts plural, 4:53 it's post singular because we're only viewing one post. 4:58 So let's save that, reload the page. 5:02 Okay, and it looks like our form rendered successfully, let's try filling it out. 5:05 Provide a name of Jay and a comment, Hi there! 5:09 Submit the form, and we get another error. 5:17 It’s trying to submit our form to the comments controller 5:20 since we’re submitting a comment. 5:23 So let’s go back to our terminal and quit out of the rails server. 5:25 And we're going to run bin/rails, generate, 5:29 controller, Comments. 5:34 That'll create a new file within our controllers folder 5:38 named comments_controller. 5:42 Since it's trying to submit a form to create a new comment, 5:44 it's going to call an action method named create. 5:47 So let's define that now, def create. 5:50 And because we said that our form is for a resource that's nested within a post, 5:56 post ID is going to be part of the form submission path. 6:01 So we'll be able to get the post ID from params post_id. 6:06 We'll need to find the post with an ID matching that parameter. 6:14 And we'll assign the post that it finds to an instance variable named post. 6:21 Now we need to use that has many association to create a new comment 6:27 that belongs to this post. 6:31 So just like we did in the console before we're going to call post.comments.create. 6:33 We're going to read this comment's parameters 6:41 from a method named comment_params. 6:45 That method doesn't exist yet though, so we'll need to create that now. 6:48 We'll create a new private method, and we'll define one named comment_params. 6:53 Here in the comment_params method we're going to use strong parameters to get 7:01 the set of parameters that we want to base our comment off of. 7:06 So we're going to take the set of all params. 7:09 We're going to require the subset that apply to the comment. 7:13 And then we're going to permit the name and 7:19 content parameters from that subset. 7:23 That'll be returned back up here and used as arguments to the create method. 7:30 And we'll wind up with a comment that has the parameters specified from our form. 7:35 And that belongs to the post here in the post variable. 7:41 We'll assign the results of that to a new instance variable named comment. 7:44 And now that we've saved the comment for our database, 7:51 we're going to want to show it in our browser. 7:53 We want to show it in the context of the post that it belongs to. 7:55 So instead of the individual comment, we're going to redirect_to, the post. 7:59 Okay, let's rerun our rails server and then go back to the browser. 8:06 Reload the page and let's try creating a comment again, see if it works this time. 8:13 We'll use a Name of Jay and Comment content of, Hi there! 8:19 Submit the form, and there's our new comment, Jay says, Hi there! 8:25 Excellent, we're able to create comments that belong to a post now. 8:32 We don't have a way to update comments once they're created, though. 8:36 We'll look at doing that next. 8:39