interesting rails association challenge

Question

I have stumbled on an interesting challenge regarding active record associations:

I have an Account model which can have multiple and different organisations attached to it (like for example a Company, a Contractor, a Person) and it also has a different role with each association (accountant, owner, viewer, etc.).

So I am not sure whats the best way to associate them.

Answer 1

Use polymorphic association to attach different types of organisations. Something like

class Account < ActiveRecord::Base
  has_many :organizations
end

class Organization < ActiveRecord::Base
  belongs_to :account
  has_many :organizations
end

class Company < ActiveRecord::Base
  belongs_to :organization, :polymorphic => true
end

class Contractor < ActiveRecord::Base
  belongs_to :organization, :polymorphic => true
end

class Person < ActiveRecord::Base
  belongs_to :organization, :polymorphic => true
end

Just off top of my head. May need some tweaking. Regarding your role - add role_id or role string to Organization model.

Answer 2

Have you had a look at Polymorphic Associations?

Answer 3

so I think I found the best solution for this, which is to use Multi Table Inheritance, for anyone interested, here's a link http://mediumexposure.com/multiple-table-inheritance-active-record/

Answer 4

I'm taking Elimantas' example, corrected some logic errors. basically, you have an Account with N Organizations (which is a polymorphic model and has relation with one of Company, Contractor, etc...)

class Account < ActiveRecord::Base
  has_many :organizations
end

class Organization < ActiveRecord::Base
  belongs_to :account
  belongs_to :resource, :polymorphic => true
end

class Company < ActiveRecord::Base
  has_many :organizations, :as => :resource
end

class Contractor < ActiveRecord::Base
  has_many :organizations, :as => :resource
end

[...etc...]

EDIT: here's the same approach to manage Roles:

# just edited Account model with role.
class Account < ActiveRecord::Base
  has_many :organizations
  has_one :role
end

class Role < ActiveRecord::Base
  belongs_to :account
  belongs_to :resource, :polymorphic => true
end

class Accountant < ActiveRecord::Base
  has_one :role, :as => :resource
end

class Owner < ActiveRecord::Base
  has_one :role, :as => :resource
end

EDIT2:

thirth edit, now the relation is: Account has_many Organizations, each Organization has_one Role, an Account has_many Roles through Organizations

class Account < ActiveRecord::Base
  has_many :organizations
  has_many :roles, :through => :organizations
end

class Role < ActiveRecord::Base
  belongs_to :resource, :polymorphic => true
end

class Accountant < ActiveRecord::Base
  has_one :role, :as => :resource
end

class Owner < ActiveRecord::Base
  has_one :role, :as => :resource
end

is this right?

EDIT3: Role as non AR model:

It may depend by how many Roles you plan to have, or you may have a name:string field where specify 'Accountant', 'Owner', and so on.

if you don't plan to put Role as AR model, then you can define an integer column called 'role_id' and use a costant with an hash in the organization model:

class Organization < ActiveRecord::Base
   belongs_to :account

   ROLES={'Accountant' => 1, 'Owner' => 2 }

   # get role as literal name
   def role
      ROLES.invert[role_id]
   end
end

this way you'll have an Account with many Organizations, each of them with a specific Role regarding that specific Account.

EDIT4: code example of EDIT3 the following code is a raw example of how it might look this association:

# new account
a = Account.new(....)
# new company & organization with a role
comp = Company.create(....)
org1 = Organization.new(:role_id => 1, ....)
org1.resource = comp

# new Contractor & Organization with another role
contr = Contractor.create(....)
org2 = Organization.new(:role_id => 2, ....)
org2.resource = contr

a.organizations << org1
a.organizations << org2

# save Account, it will have 2 different organizations, each one with a specific role
a.save