Assembling relations of multiple models in rails - impossible?

Question

Let's say I have three models.

User, Tool and Work (actually the models are different but for simplicity sake it's these guys). Now..

I User is given Tool and Tool does some Work.

User has many Tools
every Tool belongs to one User

Tool has many Works
every Work was done with single Tool

I can successfully get User.tools but I can't get the Works done by user.

I tried:

User.tools.each do |tool|
  tool.works.each do |work|
    <%= work.id %>
  end
end

but that did not exactly go as expected (multiple id's of Works a User has done), instead I got error...

What do I do wrong?

Answer 1

You can create a many-to-many association for the same :

class User <  ActiveRecord::Base
  has_many :tools
  has_many :tasks , :through => :tools, :source => :works
end

class Tool <  ActiveRecord::Base
  belongs_to :user
  has_many :works
end

class Work <  ActiveRecord::Base
  belongs_to :tool
end

Now you can do :

@users = User.all
@users.each do |user|
  user.tasks do |task|
    <%= task.id %>
  end
end

Make sure, the migration is correct. All the foreign_key/primary key relationship should be correct, otherwise you will get undefined column error. Check the #has_many official doc to understand the options I passed with the has_many method call.