Module | ActiveModel::AttributeMethods |
In: |
lib/active_model/attribute_methods.rb
|
ActiveModel::AttributeMethods provides a way to add prefixes and suffixes to your methods as well as handling the creation of Active Record like class methods such as table_name.
The requirements to implement ActiveModel::AttributeMethods are to:
A minimal implementation could be:
class Person include ActiveModel::AttributeMethods attribute_method_affix :prefix => 'reset_', :suffix => '_to_default!' attribute_method_suffix '_contrived?' attribute_method_prefix 'clear_' define_attribute_methods ['name'] attr_accessor :name private def attribute_contrived?(attr) true end def clear_attribute(attr) send("#{attr}=", nil) end def reset_attribute_to_default!(attr) send("#{attr}=", "Default Name") end end
Notice that whenever you include ActiveModel::AttributeMethods in your class, it requires you to implement a attributes methods which returns a hash with each attribute name in your model as hash key and the attribute value as hash value.
Hash keys must be strings.
respond_to? | -> | respond_to_without_attributes? |
A Person object with a name attribute can ask person.respond_to?(:name), person.respond_to?(:name=), and person.respond_to?(:name?) which will all return true. |
Allows access to the object attributes, which are held in the @attributes hash, as though they were first-class methods. So a Person class with a name attribute can use Person#name and Person#name= and never directly use the attributes hash — except for multiple assigns with ActiveRecord#attributes=. A Milestone class can also ask Milestone#completed? to test that the completed attribute is not nil or 0.
It‘s also possible to instantiate related objects, so a Client class belonging to the clients table with a master_id foreign key can instantiate master through Client#master.