module ActiveModel::API

Includes the required interface for an object to interact with Action Pack and Action View, using different Active Model modules. It includes model name introspections, conversions, translations, and validations. Besides that, it allows you to initialize the object with a hash of attributes, pretty much like Active Record does.

A minimal implementation could be:

class Person
  include ActiveModel::API
  attr_accessor :name, :age
end

person = Person.new(name: 'bob', age: '18')
person.name # => "bob"
person.age  # => "18"

Note that, by default, ActiveModel::API implements persisted? to return false, which is the most common case. You may want to override it in your class to simulate a different scenario:

class Person
  include ActiveModel::API
  attr_accessor :id, :name

  def persisted?
    self.id.present?
  end
end

person = Person.new(id: 1, name: 'bob')
person.persisted? # => true

Also, if for some reason you need to run code on initialize ( ::new ), make sure you call super if you want the attributes hash initialization to happen.

class Person
  include ActiveModel::API
  attr_accessor :id, :name, :omg

  def initialize(attributes={})
    super
    @omg ||= true
  end
end

person = Person.new(id: 1, name: 'bob')
person.omg # => true

For more detailed information on other functionalities available, please refer to the specific modules included in ActiveModel::API (see below).