has_many relation doesn't seems right or logical in business perceptive, needed some thing like belongs_to_many?

Question

My situation is like this. Company has many users and users may belongs to many companies. And current implementation is something like below.

  class Company 
    has_many :employments
    has_many :users, :through => :employments
  end

  class Employment 
    belongs_to :company
    belongs_to :user
  end

  class User
    has_many :employments
    has_many :companies, :through => :employments  #This doesn't looks correct
  end

It works, but "user has many companies" doesn't looks logically meaningful. It must be some thing like belongs_to_many companies. Do I need to use has_and_belongs_to_many?

Can some one please suggest the right way for representing these relationships?

Answer 1

If you are not going to add some special behaviour to Employment class and you don't really need it, then you should propably better use has_and_belongs_to_many. This way it will still have some table called CompanyUser, but there will not be any such class in the code.

Added: There are just 3 possbile conections between 2 objects: 1-to-1, 1-to-many and many-to-many. Rails indicates with has_* or belongs_to what of the 2 objects will get a foreign key. So:

• 1-to-1:

  has_one and belongs_to are used. The object with belongs_to gets the FK.

• 1-to-many:

  has_many and belongs_to are used. The object with belongs_to gets the FK.

• many-to-many:

  has_many[through] or has_and_belongs_to_many are used in both objects. No-one gets a FK, instead a ConnectionTable is used.

So there is no such thing as belongs_to_many, because it would be the same as has_many - providing the same relation 1-to-many.