Active Model Serialization

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

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"}

You need to declare an attributes hash which contains the attributes you want to serialize. 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.

Most of the time though, you will want to include the JSON or XML serializations. Both of these modules automatically include the ActiveModel::Serialization module, so there is no need to explicitly include it.

A minimal implementation including XML and JSON would be:

class Person
  include ActiveModel::Serializers::JSON
  include ActiveModel::Serializers::Xml

  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.to_xml              # => "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<serial-person...

person.name = "Bob"
person.serializable_hash   # => {"name"=>"Bob"}
person.as_json             # => {"name"=>"Bob"}
person.to_json             # => "{\"name\":\"Bob\"}"
person.to_xml              # => "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<serial-person...

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"}

Source: show | on GitHub 

# File activemodel/lib/active_model/serialization.rb, line 97
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) if respond_to?(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