Rails - Aug 2006 - has_many relationships - use variable of calling class?

Hi all,

I''m having trouble issuing what I consider to be a simple one to many 
relationship in rails. Here''s some code:

def SoccerPlayer < ActiveRecord::Base
  has_many :goal_list, :class_name => ''Goal'', :foreign_key
=>
''player_id'', :conditions => ''player_name =
#{last_name}''
end

Basically, I want goal_list to be a list of all goals scored by this 
player. However, accessing goal_list gives me the following error.

"undefined method `last_name'' for Goal:Class"

So #{last_name} is referencing a Goal class, and not a SoccerPlayer 
class. How do I get Rails to use the variable I want? Using 
#{SoccerPlayer.last_name} doesn''t work either ...

"undefined method ''last_name'' for
SoccerPlayer:Class" -- but I clearly
access this variable further below on the page.

Ideas?

Thanks,
Ben


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Hi --

On Mon, 28 Aug 2006, Ben wrote:
>
> Hi all,
>
> I''m having trouble issuing what I consider to be a simple one to
many
> relationship in rails. Here''s some code:
>
> def SoccerPlayer < ActiveRecord::Base
>  has_many :goal_list, :class_name => ''Goal'',
:foreign_key =>
> ''player_id'', :conditions => ''player_name =
#{last_name}''
> end
This is a bit garbled.  You need class, not def (def is for method
definitions), and the semantics are wrong: you don''t (I assume) want a
player to have many goal *lists*, but to have one list which has many
*goals*.

Also, you''re doing too much work.  If you use a foreign key to
associate the goal with the player, then you don''t also need to check
the last name -- and last names tend not to be unique anyway.
> Basically, I want goal_list to be a list of all goals scored by this
> player. However, accessing goal_list gives me the following error.
>
> "undefined method `last_name'' for Goal:Class"
>
> So #{last_name} is referencing a Goal class, and not a SoccerPlayer
> class. How do I get Rails to use the variable I want? Using
> #{SoccerPlayer.last_name} doesn''t work either ...
>
> "undefined method ''last_name'' for
SoccerPlayer:Class" -- but I clearly
> access this variable further below on the page.
>
> Ideas?
I would start with this, and then tweak incrementally as necessary if
you want to change model or association names:

1. In the database, make sure the goals table has a soccer_player_id field.
2. In soccer_player.rb (the model file), do this:

   class SoccerPlayer < ActiveRecord::Base
     has_many :goals
   end

3. In goal.rb, do this:

   class Goal < ActiveRecord::Base
     belongs_to :soccer_player
   end

4. Now, when a goal is scored, in your controller you would do this
(assuming that @player is the scorer and @goal is the goal):

   @player.goals << @goal


David

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> >
> > def SoccerPlayer < ActiveRecord::Base
> >  has_many :goal_list, :class_name => ''Goal'',
:foreign_key =>
> > ''player_id'', :conditions => ''player_name
= #{last_name}''
> > end
>
> This is a bit garbled.  You need class, not def (def is for method
> definitions), and the semantics are wrong: you don''t (I assume)
want a
> player to have many goal *lists*, but to have one list which has many
> *goals*.
>
> Also, you''re doing too much work.  If you use a foreign key to
> associate the goal with the player, then you don''t also need to
check
> the last name -- and last names tend not to be unique anyway.
>
Just for OP''s reference, the :conditions parameter is useful for doing
things like :conditions=>''deleted = true'' or similar, not
to model the
relationship itself, AR should take care of that.

Max

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