Rails - Multiple foreign keys to the same table

Question

I have 2 models, Users and Tasks

They are associated as given below :

class User < ActiveRecord::Base
    has_many :tasks, foreign_key: "assigned_to"
end

The schema of the tasks model is given below :

    t.string   "taskable_type", limit: 255
    t.integer  "taskable_id"
    t.string   "title",         limit: 255
    t.text     "description"
    t.integer  "added_by"
    t.integer  "assigned_to"
    t.datetime "due_date"
    t.datetime "created_at"
    t.datetime "updated_at"
    t.datetime "completed_at"
    t.datetime "deleted_at"

I would also like to associate the field added_by to the users table.

How would I go about this?

Answer 1

You can add a second association, you just need to give it a unique name, such as:

class User < ActiveRecord::Base
  has_many :tasks, foreign_key: "assigned_to"
  has_many :added_tasks, foreign_key: "added_by", class_name: "Task"
end

You have to add the option class_name: "Task" in this case because the proper class name cannot be inferred from the association name "added_tasks" (it would look for a class named "AddedTask").

The documentation for has_many lists the options to guide you through this sort of thing.