Custom db entry for 3 way habtm in ROR

Question

I am converting an existing perl gtk app into a ROR app

I have a 3 way habtm association model.

class CustomerMaster < ActiveRecord::Base
  has_an         


        

Answer 1

Assume you are using Rails 3.

You should use habtm when your join table has only 2 foreign keys. For most cases, has_many :through will be more flexible.

In your case, you should create a model for the join table. First, you should disable pluralization for legacy DB schema. (I thought you already did that).

# In config/application.rb
config.active_record.pluralize_table_names = false

Create a join table, namely CustomerPhoneAddress by convention (I will give it a more meaningful name):

# customer_phone_address.rb
class CustomerPhoneAddress < ActiveRecord::Base
  belongs_to :address_master
  belongs_to :customer_master
  belongs_to :phone_master
end

Finally, associate your models with has_many and has_many :through:

# address_master.rb
class AddressMaster < ActiveRecord::Base
  has_many :customer_phone_addresses
  has_many :customer_masters, :through => :customer_phone_addresses
  has_many :phone_masters, :through => :customer_phone_addresses
end

# customer_master.rb
class CustomerMaster < ActiveRecord::Base
  has_many :customer_phone_addresses
  has_many :address_masters, :through => :customer_phone_addresses
  has_many :phone_masters, :through => :customer_phone_addresses
end

# phone_master.rb
class PhoneMaster < ActiveRecord::Base
  has_many :customer_phone_addresses
  has_many :customer_masters, :through => :customer_phone_addresses
  has_many :phone_masters, :through => :customer_phone_addresses
end

I tested the code and it works very well. To create an association:

CustomerPhoneAddress.create(
  :phone_master => PhoneMaster.first,
  :address_master => AddressMaster.first,
  :customer_master => CustomerMaster.first)

To query the association:

IRB> a = AddressMaster.first
=> #<AddressMaster id: 1, created_at: "2011-12-07 15:23:07", updated_at: "2011-12-07 15:23:07">
IRB> a.customer_masters
=> [#<CustomerMaster id: 1, created_at: "2011-12-07 15:23:15", updated_at: "2011-12-07 15:23:15">]
IRB> a.phone_masters
=> [#<PhoneMaster id: 1, created_at: "2011-12-07 15:23:19", updated_at: "2011-12-07 15:23:19">]
IRB> a.customer_phone_addresses
=> [#<CustomerPhoneAddress id: 1, address_master_id: 1, customer_master_id: 1, phone_master_id: 1, created_at: "2011-12-07 15:24:01", updated_at: "2011-12-07 15:24:01">]