Rails: ActiveRecord::HasManyThroughSourceAssociationNotFoundError: Could not find the source association(s)

Question

I have the following code (somewhat simplified ...

create_table :signatures do |t|
  t.integer :signer_id
  t.integer :card_id

  t.timestamps
end

With the models looking like ...

class Signature < ActiveRecord::Base
    belongs_to :card
    belongs_to :user
end

class Card < ActiveRecord::Base
    has_many :signatures
    has_many :signers, :through => :signatures, :foreign_key => "card_id"
end


class User < ActiveRecord::Base

    has_many :sent_cards, :class_name => "Card", :foreign_key => "sender_id"
    has_many :received_cards, :class_name => "Card", :foreign_key => "recipient_id"

    has_many :signatures
    has_many :signed_cards, :through => :signatures, :foreign_key => "signer_id"

end

I see the following error using the rails console ...

ruby-1.9.2-p0 > u15.signed_cards
ActiveRecord::HasManyThroughSourceAssociationNotFoundError: Could not find the source association(s) :signed_card or :signed_cards in model Signature. Try 'has_many :signed_cards, :through => :signatures, :source => <name>'. Is it one of :card or :user?
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.1.0/lib/active_record/reflection.rb:517:in `check_validity!'
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.1.0/lib/active_record/associations/association.rb:27:in `initialize'
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.1.0/lib/active_record/associations/collection_association.rb:24:in `initialize'
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.1.0/lib/active_record/associations.rb:164:in `new'
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.1.0/lib/active_record/associations.rb:164:in `association'
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.1.0/lib/active_record/associations/builder/association.rb:41:in `block in define_readers'
    from (irb):11
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.1.0/lib/rails/commands/console.rb:45:in `start'
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.1.0/lib/rails/commands/console.rb:8:in `start'
    from /home/slabounty/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.1.0/lib/rails/commands.rb:40:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'

I get the same thing when I do add the source => :card/:user (should be :card in this case I believe).

Any ideas what I'm doing wrong here?

---

Showing a partial solution because I wanted to clean up a few things. The migration remained the same as the previous version. I'm now seeing a SQL error (see below) where it can't find user_id in Signature. I hate to say it, but mostly I've been putting in :foreign_key whereever I think they might help to no avail.

    class Signature < ActiveRecord::Base
        belongs_to :card
        belongs_to :signer, :class_name => "User"
    end


    class Card < ActiveRecord::Base
        # Correct
        has_many :signatures
        has_many :signers, :through => :signatures, :source => :user

    end

    class User < ActiveRecord::Base
        # Wrong!
        has_many :signatures, :foreign_key => "signer_id"
        has_many :signed_cards, :through => :signatures, :source => :card
    end

With the error (minus stack trace)

ruby-1.9.2-p0 >   u15.signed_cards
  Card Load (0.5ms)  SELECT "cards".* FROM "cards" INNER JOIN "signatures" ON "cards"."id" = "signatures"."card_id" WHERE "signatures"."user_id" = 15 ORDER BY cards.created_at DESC
SQLite3::SQLException: no such column: signatures.user_id: SELECT "cards".* FROM "cards" INNER JOIN "signatures" ON "cards"."id" = "signatures"."card_id" WHERE "signatures"."user_id" = 15 ORDER BY cards.created_at DESC
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: signatures.user_id: SELECT "cards".* FROM "cards" INNER JOIN "signatures" ON "cards"."id" = "signatures"."card_id" WHERE "signatures"."user_id" = 15 ORDER BY cards.created_at DESC

Card.signers returns an empty array as expected.

Still looking for some help on this one. I haven't been able to locate much in the way of simple, straightforward explanations of this where you're not using the same names (i.e. you need a foreign_key and source.

Answer 1

User should be defined like this:

class User < ActiveRecord::Base

  has_many :sent_cards, :class_name => "Card", :foreign_key => "sender_id"
  has_many :received_cards, :class_name => "Card", :foreign_key => "recipient_id"

  has_many :signatures
  has_many :signed_cards, :through => :signatures, :source => :card

end

When your association name is different than the name used at the :through you have to define the source parameter. If you look at the exception message it explicitly asks you to do it.

Answer 2

OK, since I had such a hard time with this, I wanted to show everyone what the final version looked like. A good part of the reason I had such a hard time firguring this out, was the fact that the rails console didn't seem to be reloading things correctly as I made changes. I didn't realize this until I gave up one night, came back the next morning and the case that had been working the previous night wasn't and the case that wasn't working was.

The migration is the same, but I'll repeat it for completeness sake.

def change
    create_table :signatures do |t|
        t.integer :signer_id
        t.integer :card_id
        t.boolean :signed,    :default => false
        t.text :message

        t.timestamps
    end
end

The Signature class has the two belongs_to with card being the case that normally gets shown in the examples and the signer being of type user.

class Signature < ActiveRecord::Base
    belongs_to :card
    belongs_to :signer, :class_name => "User"
end

The User has many signatures (necessary even if you don't use them directly) an dmany signed_cards through signatures with a source of card (telling Rails which class type the signed_cards are.

class User < ActiveRecord::Base
    has_many :signatures, :foreign_key => "signer_id"
    has_many :signed_cards, :through => :signatures, :source => :card 
end

Finally, the Card has many signatures (once again necessary) and many signers through signatures and the foreign_key for the signer of signer_id.

class Card < ActiveRecord::Base
    has_many :signatures
    has_many :signers, :through => :signatures, :foreign_key => 'signer_id'
end

Hopefully, this will help others having similar issues.