form_for - Child object - how to set parent id

rubyonrails-talk
1

D L wrote:

So you can see I have a form for block to handle the comments entry - but if I have multiple blogs on a single page how can I specify that this particular comment relates to blog X? If I only have one blog per page I can get away with storing the blog id in the session, but this seems a bit messy.

Hi D L,

(Welcome to Rails, by the way).

The key is to learn about how to specify the relationships between your models. In your comment model, indicate that it's parent object is a Blog:

class Comment < ActiveRecord::Base ... belongs_to :blog

end

Now, anytime you have a Comment object, you can use comment.blog to "get back" to the parent blog object.

Does this help? If I misunderstood the question somehow, let me know.

Jeff www.softiesonrails.com

2

Have you thought about using Ajax to create the form on the fly, thereby making the ownership of the comment clearer?

D L-3 wrote:

3

> The problem is that I can not see any way to set the BlogId (parent) on > the comment. So I have code in my controller that looks like this: > > def add_comment > @comment = Comment.new(params[:comment]) > @comment.blog_id = ??? <- Where do I get this from??? > if @comment.save > flash[:notice] = "Thank you for your comment" > end > list > render :action => 'list' > end >

From your view code I assume that you create one blank comment in your controller and are trying to reuse that?

A better way may be to add a new_comment method to the blog model:

def new_comment   Comment.new( :blog=>self ) end

and then use

<%= form_for :comment, blog.new_comment, :url=>... %> <%= form.hidden_field :blog_id %>

If you want to stick with the one-template-comment approach, do something like

<%= hidden_field :comment, :blog_id, :value=>blog.id %>

Cheers, Max