Rails - Apr 2011 - a nil object when you didn't expect it!

I''m a new ruby, now i have a newbie problem

I have three model
1.
[code]
class SfProduct < ActiveRecord::Base
  has_many :sf_actions_maps
    def sf_add_user_to_action_map()
    sf_actions_maps << SfProductMap.new()
  end
end
[/code]
2.
[code]
class SfProductMap < ActiveRecord::Base
  belongs_to :sf_product
  belongs_to :sf_user
[/code]
3.
[code]
class SfUser < ActiveRecord::Base
  has_many :sf_products_maps
[/code]

product controller create code :
 def create
    @sf_product = SfProduct.new()
    @sf_product.sf_add_user_to_action_map(@sf_user)
    respond_to do |format|
      if @sf_activity.save

      else

      end
    end


afert user the create actions, the error will be show:

You have a nil object when you didn''t expect it!
You might have expected an instance of ActiveRecord::Base.
The error occurred while evaluating nil.delete

please help me!

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On 15 April 2011 11:08, seth shao
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> I''m a new ruby, now i have a newbie problem
>
> I have three model
> 1.
> [code]
> class SfProduct < ActiveRecord::Base
>  has_many :sf_actions_maps
>    def sf_add_user_to_action_map()
>    sf_actions_maps << SfProductMap.new()
>  end
> end
> [/code]
> 2.
> [code]
> class SfProductMap < ActiveRecord::Base
>  belongs_to :sf_product
>  belongs_to :sf_user
> [/code]
> 3.
> [code]
> class SfUser < ActiveRecord::Base
>  has_many :sf_products_maps
> [/code]
>
> product controller create code :
>  def create
>    @sf_product = SfProduct.new()
>    @sf_product.sf_add_user_to_action_map(@sf_user)
>    respond_to do |format|
>      if @sf_activity.save
>
>      else
>
>      end
>    end
>
>
> afert user the create actions, the error will be show:
>
> You have a nil object when you didn''t expect it!
> You might have expected an instance of ActiveRecord::Base.
> The error occurred while evaluating nil.delete
The error message should tell you which line of your code is failing.
On that line you have probably used a variable that is nil.  Possibly
you have done a find and it has not found any records.

If you can''t see it post the whole error message and stack trace and
the bit of code around the error.

Colin

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