Forum: Ruby on Rails I am getting a ' undefined method error ' when saving a comment

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5692fecdbae1e474560268b6843c2c41?d=identicon&s=25 ank k. (Guest)
on 2013-08-22 21:56
hi!! I am a newbie in ROR.

I have two models

has_many :Comment

belongs_to :Post

the error displays when I try to save a comment related to certain post.
I get the following error
undefined method `comment' for nil:NilClass
my comment controllers

  def new
 @comment =
render :layout => false

  def create
    @post = Post.find_by_id(params[:id])
    @post_comment = @post.comment.create(params[:comment])
      redirect_to post_index_path
      flash[:success] = "comment created!!"

Could someone please explain why am I getting this error..

Thanks in advance :)
Germano T. (Guest)
on 2013-08-22 22:07
(Received via mailing list)
You shold use

*has_many :comments*

instead of

*has_many :comment*

Then you can call


Look this example:

Take a look at accepts_nested_attributes to create your posts:

2013/8/22 ank k. <removed_email_address@domain.invalid>
Colin L. (Guest)
on 2013-08-22 22:09
(Received via mailing list)
On 22 August 2013 20:56, ank k. <removed_email_address@domain.invalid> wrote:
> hi!! I am a newbie in ROR.
> I have two models
> Post
> has_many :Comment

that should be
has_many :comments
note that it is plural and lower case
> Comment
> belongs_to :Post

belongs_to :post

>  @comment =
> render :layout => false
>   end
>   def create
>     @post = Post.find_by_id(params[:id])
>     @post_comment = @post.comment.create(params[:comment])

You have not told us which line the error points to but I guess it is
the one above.  If so then it is saying that @post is nil, so your
find_by_id did not find anything.  You don't need to use find_by_id,
you can just use
@post = Post.find( params[:id] )
Perhaps there is not a Post object with the correct id.  If you look
in log/development.log you will see the params you are passing which
may give you a clue.

I suggest, however, that as a beginner you work right through a good
tutorial such as (which is free to use online).
That will show you the basics of rails.

Also see the Rails Guides.

311b3053c29f690eb194ce525a2b6b18?d=identicon&s=25 John W. (Guest)
on 2017-03-21 10:23
Thank you support.
1a386d839c10ef7306c13ef5b2c822f1?d=identicon&s=25 Max P. (Guest)
on 2017-04-18 13:55
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