Question

I’m new to rails and like many I seem to be having challenges figuring out how ActiveRecord and associations work.

I have three models, user, projects and tasks:

Class User < ActiveRecord::Base
    has_many :projects
    has_many :tasks
end

Class Project < ActiveRecord::Base
    has_many :tasks
    belongs_to :user
end

Class Task < ActiveRecord::Base
    belongs_to :projects
    belongs_to :user
end

Both Projects and Tasks both have the field user_id. Tasks has the field project_id.

I expect to be able to look up all the Projects and Tasks through the user. However, every time I try, I get a blank array even though there are Projects and Tasks:

usr = User.find(1)
=> [User id: 1, name: "Some Guy"]
usr.projects
=> []
usr.tasks
=> []

It does work when I query for Tasks through Projects:

proj = Project.find(1)
=> [#<Project id: 1, user_id: 1, description: "Some Project">]
proj.tasks
=> [#<Task id: 1, user_id: 1, project_id: 1, description: "Do Something">, 
   #<Task id: 2, user_id: 1, project_id: 1, description: "Do another thing">]

I believe that the has_many and belongs_to settings are correct since I have other models connected to the User and they work correctly. Any ideas what I’m missing?

Answer 1

I figured it out by changing the model associations. I removed the belongs_to :user from the Task model and added a has_many :through relationship to the User model:

Class User < ActiveRecord::Base
    has_many :projects
    has_many :tasks, :through => :projects
end

Class Project < ActiveRecord::Base
    has_many :tasks
    belongs_to :user
end

Class Task < ActiveRecord::Base
    belongs_to :projects
end

After restarting the console, I can now pull up tasks that belong to the user in the way I was originally trying:

usr = User.find(1)
usr.projects
=>[#<Project id: 1, user_id: 1, description: "Some Project">]
usr.tasks
=>[#<Task id: 1, project_id: 1, description: "Do Another Thing">]