Association of User roles

1.User

User Roles belongs to exactly one user. It also has polymorphic associations with "granted by user" and "revoked by user" with class name User.

belongs_to  :user

# Every user role can have a granted by user
belongs_to  :granted_by_user, :class_name => "User", :foreign_key => :granted_by_user_id

  # Every user role can have a revoked by user
belongs_to  :revoked_by_user, :class_name => 'User', :foreign_key => :revoked_by_user_id

2.Role

Every User Role belongs to exactly one role.

# Every user role belongs to exactly one role
belongs_to  :role