Posting comments from the show action of another controller

Question

I have a typical blog app where users can post comments from the Posts#show template.

resources :posts do
  resources :comments
end

# posts_controller.rb
def show
  @post = Post.find(params[:id])
  @comment = @post.comments.build
end
# comments_controller.rb
def create
  @post = Post.find(params[:post_id])
  @comment = @post.comments.build(params[:comment])
  @comment.author = current_user
  if @comment.save
    redirect_to @post
  else
    render 'posts/show'
  end
end

In the view, I'm first checking if there are comments, outputting them, and then I'm displaying a new comment form.

/ posts/show.html.slim
- if @post.comments.any?
  @post.comments.each do |comment|
    p = comment.author.name
...
= form_for [@post, @comment]

If comment validation fails, I get a 'no method name for nil class' error. I think this is because @post.commets.any? returns true since the comment was built through the post association--even though the comment failed validation and did not get saved.

How do you work around this?

Answer 1

When the comment validation fails, comment.author might not be set and hence will be nil. This explains the nil.name error.

You could try something like

@post.comments.each do |comment|
   p = comment.author.try(:name)

OR

@post.comments.each do |comment|
  unless comment.new_record?
    p = comment.author.try(:name)
  end
end

OR

@post.comments.reject{|c| c.new_record?}.each do |comment|
  p = comment.author.try(:name)
end

Answer 2

Change

if @post.comments.any?

To

if @post.comments.blank?

and check again.

Answer 3

Without knowing what your posts and comments models look like, it's a bit hard to pin-point the problem, but here's how I would solve your problem:

# app/models/post.rb
has_many :comments

# app/models/comment.rb
belongs_to :post

# app/controllers/posts_controller.rb
def show
  @post = Post.find params[:id]
end

# app/controllers/comments_controller.rb
def create
  # No need to instantiate the post and build the comment on it here since
  # we're going to set the post_id on the comment form.

  @comment = Comment.new params[:comment]
  if @comment.save
    # ...
  else
    # ...
  end
end

# app/views/posts/show.html.slim
- if @post.comments.any?
  @post.comments.each do |comment|
    # ...

- form_for Comment.new do |f|
  = f.text_field :author
  = f.text_field :body
  # ...
  = f.hidden_field :post_id, @post.id # This passes the comment's related post_id on to the controller.
  = f.submit

I don't know if the Slim section is syntactically correct - I haven't yet used the templating engine.

Please note that this isn't production safe code! I've omitted a lot of formalities in order to keep the example short and (hopefully) to the point.