ActiveModel::Serialization

Active Model Serialization

Provides a basic serialization to a #serializable_hash for your objects.

A minimal implementation could be:

class Person
  include ActiveModel::Serialization

  attr_accessor :name

  def attributes
    {'name' => nil}
  end
end

Which would provide you with:

person = Person.new
person.serializable_hash   # => {"name"=>nil}
person.name = "Bob"
person.serializable_hash   # => {"name"=>"Bob"}

An attributes hash must be defined and should contain any attributes you need to be serialized. Attributes must be strings, not symbols. When called, serializable hash will use instance methods that match the name of the attributes hash's keys. In order to override this behavior, take a look at the private method read_attribute_for_serialization.

ActiveModel::Serializers::JSON module automatically includes the ActiveModel::Serialization module, so there is no need to explicitly include ActiveModel::Serialization.

A minimal implementation including JSON would be:

class Person
  include ActiveModel::Serializers::JSON

  attr_accessor :name

  def attributes
    {'name' => nil}
  end
end

Which would provide you with:

person = Person.new
person.serializable_hash   # => {"name"=>nil}
person.as_json             # => {"name"=>nil}
person.to_json             # => "{\"name\":null}"

person.name = "Bob"
person.serializable_hash   # => {"name"=>"Bob"}
person.as_json             # => {"name"=>"Bob"}
person.to_json             # => "{\"name\":\"Bob\"}"

Valid options are :only, :except, :methods and :include. The following are all valid examples:

person.serializable_hash(only: 'name')
person.serializable_hash(include: :address)
person.serializable_hash(include: { address: { only: 'city' }})
Methods
S
Instance Public methods
serializable_hash(options = nil)

Returns a serialized hash of your object.

class Person
  include ActiveModel::Serialization

  attr_accessor :name, :age

  def attributes
    {'name' => nil, 'age' => nil}
  end

  def capitalized_name
    name.capitalize
  end
end

person = Person.new
person.name = 'bob'
person.age  = 22
person.serializable_hash                # => {"name"=>"bob", "age"=>22}
person.serializable_hash(only: :name)   # => {"name"=>"bob"}
person.serializable_hash(except: :name) # => {"age"=>22}
person.serializable_hash(methods: :capitalized_name)
# => {"name"=>"bob", "age"=>22, "capitalized_name"=>"Bob"}

Example with :include option

class User
  include ActiveModel::Serializers::JSON
  attr_accessor :name, :notes # Emulate has_many :notes
  def attributes
    {'name' => nil}
  end
end

class Note
  include ActiveModel::Serializers::JSON
  attr_accessor :title, :text
  def attributes
    {'title' => nil, 'text' => nil}
  end
end

note = Note.new
note.title = 'Battle of Austerlitz'
note.text = 'Some text here'

user = User.new
user.name = 'Napoleon'
user.notes = [note]

user.serializable_hash
# => {"name" => "Napoleon"}
user.serializable_hash(include: { notes: { only: 'title' }})
# => {"name" => "Napoleon", "notes" => [{"title"=>"Battle of Austerlitz"}]}

Source: show | on GitHub 

# File activemodel/lib/active_model/serialization.rb, line 124
def serializable_hash(options = nil)
  options ||= {}

  attribute_names = attributes.keys
  if only = options[:only]
    attribute_names &= Array(only).map(&:to_s)
  elsif except = options[:except]
    attribute_names -= Array(except).map(&:to_s)
  end

  hash = {}
  attribute_names.each { |n| hash[n] = read_attribute_for_serialization(n) }

  Array(options[:methods]).each { |m| hash[m.to_s] = send(m) }

  serializable_add_includes(options) do |association, records, opts|
    hash[association.to_s] = if records.respond_to?(:to_ary)
      records.to_ary.map { |a| a.serializable_hash(opts) }
    else
      records.serializable_hash(opts)
    end
  end

  hash
end