Question

I’m working to install the acts_as_commentable plugin on my
Rails 3 app.

After adding “acts_as_commentable” to my book model, I then added a
comment form on my book show view:

<% form_for(@comment) do|f| %> 
  <%= f.hidden_field :book_id %> 
  <%= f.label :comment %><br /> 
  <%= f.text_area :comment %> 
  <%= f.submit "Post Comment" %> 
<% end %> 

Then in the controller (comments_controller.rb),

  def create 
    @comment = Comment.new(params[:comment]) 
    Book.comments.create(:title => "First comment.", :comment => "This 
is the first comment.") 
  end 

Then when submitting a comment, it returns the error: “unknown
attribute: book_id”
From the log:

  Processing by CommentsController#create as HTML 
  Parameters: {"comment"=>{"comment"=>"WOOOW", "book_id"=>"32"}, 
"commit"=>"Post Comment", 
"authenticity_token"=>"5YbtEMpoQL1e9coAIJBOm0WD55vB2XRZMJa4MMAR1YI=", 
"utf8"=>"✓"} 
Completed   in 11ms 
ActiveRecord::UnknownAttributeError (unknown attribute: book_id): 
  app/controllers/comments_controller.rb:3:in `new' 
  app/controllers/comments_controller.rb:3:in `create' 

Suggestions?

Answer 1

I think you have to options:

Option 1)
The view:

<% form_for(@comment) do|f| %> 
  <%= f.hidden_field :commentable_id, :value => @book.id %>
  <%= f.hidden_field :commentable_type, :value => 'Book' %> 
  <%= f.label :comment %><br /> 
  <%= f.text_area :comment %> 
  <%= f.submit "Post Comment" %> 
<% end %> 

The controller:

def create
  @comment = Comment.create(params[:comment])
end

Option 2)

In the controller:

def create
  @book = Book.find(params[:comment][:book_id])
  @comment = @book.comments.create(params[:comment].except([:comment][:book_id]))
end

I haven’t tested the code, but the idea should be correct

Update, given you want to comment on various models (i’m writting my code without testing it…). So let’s say you have Book and Magazine, and you want to comment on them. I guess I would define nested routes for them.

map.resources :books, :has_many => :comments
map.resources :magazines, :has_many => :comments

And then in your controller you could do:

before_filter :find_commentable

def find_commentable
  @commentable = Book.find(params[:book_id]) if params[:book_id]
  @commentable = Magazine.find(params[:magazine_id]) if params[:magazine_id]
end

And in the new view:

<% form_for :comment, [@commentable, @comment] do |f| %>
  <%= f.label :comment %>
  <%= f.text_area :comment %>
  <%= f.submit %>
<% end %>

So the create action could look something like:

def create
  @user.comments.create(params[:comment].merge(:commentable_id => @commentable.id, :commentable_type => @commentable.class.name))
  redirect_to @commentable
end

Maybe there are even better ways to do it…