Rails - Jul 2006 - Trouble with has_one

Hi,

I''m trying to write a blog application where each post has a single 
header image associated.

My models:
----------
class Post < ActiveRecord::Base
	belongs_to :blog
	has_many :images
	has_one  :header
end

class Header < ActiveRecord::Base
	file_column :image_path
end

class Image < ActiveRecord::Base
	belongs_to :post
	file_column :image_path
end

The controller targets I have used:
-----------------------------------

  def uploadImage
    Post.find(params[:id]).images.create(params[:image])
    @post = Post.find(params[:id])
    flash[:notice] = "Image was successfully uploaded"
    redirect_to :action => ''showBlogPosts'', :id =>
@post.blog_id
  end

  def uploadHeaderImage
    Post.find(params[:id]).header.create(params[:header])
    @post = Post.find(params[:id])
    flash[:notice] = "Image was successfully uploaded"
    redirect_to :action => ''showBlogPosts'', :id =>
@post.blog_id
  end

As you can see POST has two children, image and header.

POST (has_many) images
POST (has_one) header

When I try to create a header for a post, I get:
You have a nil object when you didn''t expect it!
You might have expected an instance of ActiveRecord::Base.
The error occured while evaluating nil.create
>From development log I could see that the SQLs built in case of has_many 
and has_one differ. has_one has LIMIT 1 attached.

Is that the reason why this is failing? How to get around this?

-- 
Posted via http://www.ruby-forum.com/.

On 7/17/06, Nishant Kyal <nishant_kyal@hotmail.com>
wrote:
>   def uploadHeaderImage
>     Post.find(params[:id]).header.create(params[:header])
You probably don''t really have a header at this point, so it will be
nil.  You should create a new Header and then assign it to the Post
instance that you get back from find().

-- James

"Nishant Kyal" <nishant_kyal@hotmail.com> wrote 
in message
news:f1c8371b25abb98c5a11949b2ef72529@ruby-forum.com...
> Hi,
>
> I''m trying to write a blog application where each post has a
single
> header image associated.
snip
>  def uploadHeaderImage
>    Post.find(params[:id]).header.create(params[:header])
>    @post = Post.find(params[:id])
>    flash[:notice] = "Image was successfully uploaded"
>    redirect_to :action => ''showBlogPosts'', :id =>
@post.blog_id
>  end
>
> When I try to create a header for a post, I get:
> You have a nil object when you didn''t expect it!
> You might have expected an instance of ActiveRecord::Base.
> The error occured while evaluating nil.create
the create syntax for has_one associations is a little different to 
has_many. Try this instead:
Post.find(params[:id]).create_header(params[:header])

You can also do something like:

h = Header.create(params[:header])
p = Post.find(params[:id])
p.header = h

hth