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require "active_support/core_ext/hash/except"
require "active_support/core_ext/hash/slice"
module ActiveModel
# == 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 <tt>ActiveModel::Serialization</tt> module, so there is no need to
# explicitly include <tt>ActiveModel::Serialization</tt>.
#
# 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 <tt>:only</tt>, <tt>:except</tt>, <tt>:methods</tt> and
# <tt>:include</tt>. The following are all valid examples:
#
# person.serializable_hash(only: 'name')
# person.serializable_hash(include: :address)
# person.serializable_hash(include: { address: { only: 'city' }})
module Serialization
# 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 <tt>:include</tt> 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"}]}
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
private
# Hook method defining how an attribute value should be retrieved for
# serialization. By default this is assumed to be an instance named after
# the attribute. Override this method in subclasses should you need to
# retrieve the value for a given attribute differently:
#
# class MyClass
# include ActiveModel::Serialization
#
# def initialize(data = {})
# @data = data
# end
#
# def read_attribute_for_serialization(key)
# @data[key]
# end
# end
alias :read_attribute_for_serialization :send
# Add associations specified via the <tt>:include</tt> option.
#
# Expects a block that takes as arguments:
# +association+ - name of the association
# +records+ - the association record(s) to be serialized
# +opts+ - options for the association records
def serializable_add_includes(options = {}) #:nodoc:
return unless includes = options[:include]
unless includes.is_a?(Hash)
includes = Hash[Array(includes).map { |n| n.is_a?(Hash) ? n.to_a.first : [n, {}] }]
end
includes.each do |association, opts|
if records = send(association)
yield association, records, opts
end
end
end
end
end
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