Rails Emirates_to和has_many外键关系

Question

I need a little help... I have these relationships... Users belong to Department, a Department has a manager, Managers (Users) can have many managed departments.

I'm having one of those days and I can't for the life of me figure out what to put inside the User model to define the `has_many :managed_departments' part of the relationship.

Department

class Department < ActiveRecord::Base
  has_many :users
  belongs_to :manager, foreign_key: "manager_id", class_name: "User"
end

User

class User < ActiveRecord::Base
  belongs_to :department
  # has_many :managed_departments
end

This works: Department.last.manager which returns:

=> #<User id: 2, etc...

I'm having a mindblank on what to put in the User model.

Can anyone help?

Answer 1

You can use class_name option same like you used it in Department model

#user.rb
class User < ActiveRecord::Base
  belongs_to :department
  has_many :managed_departments, class_name: "Department", foreign_key: "manager_id"
end

Answer 2

You are not creating right association. You have many to many relation ship between user and department.

user has_many departments (Can manage multiple department)
department has_many users

As a database standard you should break many to many relationship and introduce a new intermediate table.

So your new table should be users_departments . In this table you can add column user is manager or not.

table should have column : user_id , department_is, is_manager

class Department < ActiveRecord::Base
  has_many :users, :through => :users_departments
end

class User < ActiveRecord::Base
  has_many :departments, :through => :users_departments
end

class UsersDepartment < ActiveRecord::Base
  belongs_to :user
  belongs_to :department
end

Here you can find anything with association. and with simple scope you can find manager of department also.