Question

I have the following models associated with has_many through with conditions.

(Note that Membership validates the presence of the kind attribute)

class User < ActiveRecord::Base
  has_many :memberships
  has_many :founded_groups,
    :through => :memberships,
    :source  => :group,
    :class_name => 'Group'
    :conditions => {'memberships.kind' => 'founder'}
  has_many :joined_groups, ... # same as above, but the kind is 'member'
end

class Group < ActiveRecord::Base
  has_many :memberships
  has_many :founders, ...        # these two mirror the User's
  has_many :regular_members, ... #
end

class Membership < ActiveRecord::Base
  validates_presence_of :user_id
  validates_presence_of :club_id
  validates_presence_of :kind   # <-- attention here!

  belongs_to :user
  belongs_to :group
end

Rails seems to like the code above (at least it doesn’t bark to it). But then this happens:

> user = User.create(...) # valid user
> club = Club.create(...) # valid club
> user.founded_clubs = [club]

ActiveRecord::RecordInvalid: Validation failed: kind can't be blank

> club.founders << user

ActiveRecord::RecordInvalid: Validation failed: kind can't be blank

I was assuming that rails would take the {'memberships.kind' => 'founder'} part of my code and use it when creating the association, but it doesn’t seem to be the case. So the new membership’s kind is blank, and that throws an error.

Is there an easy way to create the associations, without it being a complete pain?

Answer 1

This will work for sure:

> user = User.create(...) # valid user
> club = Club.create(...) # valid club
> user.memberships.create(:club_id => club.id, :kind => 'founder')

I’m not sure, but this may work:

> user.memberships.create(:club => club, :kind => 'founder')