Rails - Sep 2006 - Rails newbie - can anyone please help with many to many NoMethodError

Please can someone help with the following problem -

I''m using LoginEngine and have a Users table linked many to many to a
Plants table. The joining table is plants_users with plant_id and
user_id (there are extra fields, so I''m avoiding
has_and_belongs_to_many - plus it didn''t work :().

::user.rb starts:-
class User < ActiveRecord::Base
  has_many :Plants, :through => :plants_users
...

::plant.rb is:-
class Plant < ActiveRecord::Base
 has_many :Users, :through => :plants_users
end

::plant_user.rb is:
class PlantUser < ActiveRecord::Base
 belongs_to :user
 belongs_to :plant
end

::plant_controller.rb is
class PlantController < ApplicationController
 before_filter :login_required
 scaffold :plant

 def list
  @plants = @session[''user''].plants
 end
end

So far so good (I think), but when I access this (using instantrails),
I get
NoMethodError in PlantController#list
undefined method `plants'' for #<User:0x3969fa0>
So - apparently User has no plants method - but why not - surely thats
whats rails does?! I''ve tried reading loads of tutorials, changing this
code umpteen times, using has_and_belongs_to_many and can''t seem to get
anywhere.

Please help
    Cheers
        Andy Stratton


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ssstratton wrote:
> ::user.rb starts:-
> class User < ActiveRecord::Base
>   has_many :Plants, :through => :plants_users
> ...
In your user class, you have to write the symbol :plants in lower case,
like so:

has_many :plants, :through => :plants_users

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Thanks Gernot - I''m now ''unstuck'' for the moment.
Though - I only
arranged to get the has_and_belongs_to_many version to work - but
that''s better than before.

Cheers
  Andy Stratton


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ssstratton wrote:
> Please can someone help with the following problem -
> 
> I''m using LoginEngine and have a Users table linked many to many
to a
> Plants table. The joining table is plants_users with plant_id and
> user_id (there are extra fields, so I''m avoiding
> has_and_belongs_to_many - plus it didn''t work :().
> 
> ::user.rb starts:-
> class User < ActiveRecord::Base
>   has_many :Plants, :through => :plants_users
> ...
> 
> ::plant.rb is:-
> class Plant < ActiveRecord::Base
>  has_many :Users, :through => :plants_users
> end
> 
> ::plant_user.rb is:
> class PlantUser < ActiveRecord::Base
>  belongs_to :user
>  belongs_to :plant
> end
> 
> ::plant_controller.rb is
> class PlantController < ApplicationController
>  before_filter :login_required
>  scaffold :plant
> 
>  def list
>   @plants = @session[''user''].plants
>  end
> end
> 
> So far so good (I think), but when I access this (using instantrails),
> I get
> NoMethodError in PlantController#list
> undefined method `plants'' for #<User:0x3969fa0>
> So - apparently User has no plants method - but why not - surely thats
> whats rails does?! I''ve tried reading loads of tutorials, changing
this
> code umpteen times, using has_and_belongs_to_many and can''t seem
to get
> anywhere.
> 
> Please help
>     Cheers
>         Andy Stratton
If you use a PlantUser join model for has_many :through, you can''t name
the db table plants_users, as ActiveRecord will be looking for 
plant_users (singular plant). The plants_users convention is for habtm 
only, not for hmt. It''s better to name your join model / table as a
noun
like "assignments" or "subscriptions".

I have a lot of examples and tips on using hmt and other associations on 
my blog. Here''s one to get you started:
http://blog.hasmanythrough.com/articles/2006/04/20/many-to-many-dance-off

--
Josh Susser
http://blog.hasmanythrough.com


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Thanks josh - I have has_many :through working now.

If anyone is interested, I can post abridged code - though josh''s blog
covers it nicely anyway.

Cheers
  Andy Stratton


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