inherits_values_from

This gem allows an ActiveRecord model to inherit values from another model if its own value is nil.

Installation

gem install inherits_values_from

or in your Gemfile

gem 'inherits_values_from'

Example

class User < ActiveRecord::Base
  attr_accessible :works_saturday
  belongs_to :company
  
  inherits_values_from :company, [:works_saturday]
  
end

class Company < ActiveRecord::Base
  attr_accessible :works_saturday
end

 :001 > c = Company.new(works_saturday: false)
  => #<Company ... >
 :002 > u = c.users.build(works_saturday: true)
  => #<User ... >
 :003 > u.works_saturday
  => true # the value set on `user`
 :004 > u.works_saturday = nil
  => nil # we've removed the value
 :005 > u.works_saturday
  => false # the value inherited from `company`

If the column names don't match up, for instance if on Company it's employees_work_saturday you can pass a hash instead of an array to inherits_values_from:

class User < ActiveRecord::Base
  attr_accessible :works_saturday
  belongs_to :company

  inherits_values_from :company, { :works_saturday => :employees_work_saturday }

end

class Company < ActiveRecord::Base
  attr_accessible :employees_work_saturday
end

Todo

Tests

I think I need a full dummy rails app in order to test this properly. It's planned.