Question

I have two tables with a many to many relationship, through a third table. In the third table is a piece of data I need to assign when I build the relationships between the two tables, how can I use ActiveRecords build method to assign that?

Here is code to show what I mean:

class Company < Contact

  has_many :contact_companies
  has_many :people, :through => :contact_companies
  accepts_nested_attributes_for :people, :allow_destroy => true
  accepts_nested_attributes_for :contact_companies

end


class Person < Contact

  has_many :contact_companies
  has_many :companies, :through => :contact_companies
  accepts_nested_attributes_for :companies, :allow_destroy => true
  accepts_nested_attributes_for :contact_companies
end


class ContactCompany < ActiveRecord::Base
  belongs_to :person
  belongs_to :company
end

ContactCompany contains a data member called “position”. What I want to do is something like:

c = Person.new
c.companies.build(:name => Faker::Company.name, :position => positions.sample)

EDIT:

When I try the code above I get “unknown attribute: position”.

Answer 1

The c.companies.build line is attempting to build a Company object which does not have the position attribute (the ContactCompany does) hence the error. It looks like you are trying to set attributes on two different models, so you’ll have to make sure you are setting the appropriate attribute on the right model:

# you can chain these calls but I separated them for readability
cc = c.contact_companies.build(:position => positions.sample)
cc.build_company(:name => Faker::Company.name)