attr_value_object is a minimalistic module.

attr_value_object is useful in the case when you have a model with multiple fields to represent the dependent property and you want to separate logic. For example, address of user. The fields are postcode, prefecture_id, street and building. If you are using Ruby on Rails, you will add columns into users with a migration. You may want to make them indicating explicitly a same property (address). So the User model looks like following.

# ActiveRecord is not required.
# It's enough for `attr_value_object` to work if only these accessors are defined.

class User
  attr_accessor :address_postcode,
                :address_prefecture_id,
                :address_street,
                :address_building
end

If another model has the same property (address) and you want to JOIN based on addresses, it's good to create addresses table. But there is the case you don't need such a function. However, you may still want to separate logic. Then, you can do it with creating Address class and specifying attr_value_object.

class Address
  attr_accessor :postcode,
                :prefecture_id,
                :street,
                :building
end

class User
  extend AttrValueObject

  attr_accessor :address_postcode,
                :address_prefecture_id,
                :address_street,
                :address_building

  attr_value_object :address
end

address = Address.new
address.postcode = '1000000'
address.prefecture_id = 1
address.street = 'Foo Bar Street'
address.building = 'AVO Building 34F'

user = User.new

# setter
user.address = address
user.address_postcode # => '1000000'

# getter
user.address # => #<Address> always new instance

The binding class is inferred from name unless class_name option is specified.

• work with rails validations
• attribute mapping flexibility