Active SupportCore Extensions (2)

ROR lab. DD-1- The 2nd round -

April 13, 2013

Hyoseong Choi

Ext. to Module• alias_method_chain

active_support/core_ext/module/aliasing.rb

• “alias chaining”? ➧ wrapping

http://erniemiller.org/2011/02/03/when-to-use-alias_method_chain/

ActionController::TestCase.class_eval do  def process_with_stringified_params(...)    params = Hash[*params.map {|k, v| [k, v.to_s]}.flatten]    process_without_stringified_params(action, params, session, flash, http_method)  end  alias_method_chain :process, :stringified_paramsend

Ext. to Module• alias_attribute

active_support/core_ext/module/aliasing.rb

class User < ActiveRecord::Base  # let me refer to the email column as "login",  # possibly meaningful for authentication code  alias_attribute :login, :emailend

Ext. to Module• attr_accessor_with_default

active_support/core_ext/module/attr_accessor_with_default.rb

class Url  attr_accessor_with_default :port, 80end Url.new.port # => 80

class User  attr_accessor :name, :surname  attr_accessor_with_default(:full_name) do    [name, surname].compact.join(" ")  endend u = User.newu.name = 'Xavier'u.surname = 'Noria'u.full_name # => "Xavier Noria"

not cached

Ext. to Module• attr_internal or attr_internal_accessor

active_support/core_ext/module/attr_internal.rb

# libraryclass ThirdPartyLibrary::Crawler  attr_internal :log_levelend # client codeclass MyCrawler < ThirdPartyLibrary::Crawler  attr_accessor :log_levelend

@_log_level

Module.attr_internal_naming_format = “@_%s”

sprintf-like format

Ext. to Module• attr_internal or attr_internal_accessor

active_support/core_ext/module/attr_internal.rb

module ActionView  class Base    attr_internal :captures    attr_internal :request, :layout    attr_internal :controller, :template  endend

Ext. to Module• mattr_accessor

active_support/core_ext/module/attr_accessors.rb

module ActiveSupport  module Dependencies    mattr_accessor :warnings_on_first_load    mattr_accessor :history    mattr_accessor :loaded    mattr_accessor :mechanism    mattr_accessor :load_paths    mattr_accessor :load_once_paths    mattr_accessor :autoloaded_constants    mattr_accessor :explicitly_unloadable_constants    mattr_accessor :logger    mattr_accessor :log_activity    mattr_accessor :constant_watch_stack    mattr_accessor :constant_watch_stack_mutex  endend

• cattr_accessor

Ext. to Module

• Parents

active_support/core_ext/module/introspection.rb

• parent

• parent_name

• parents

Ext. to Module• Parents

active_support/core_ext/module/introspection.rb

module X  module Y    module Z    end  endendM = X::Y::Z X::Y::Z.parent # => X::YM.parent       # => X::Y

• parent

Ext. to Module• Parents

active_support/core_ext/module/introspection.rb

• parent_name

module X  module Y    module Z    end  endendM = X::Y::Z X::Y::Z.parent_name # => "X::Y"M.parent_name       # => "X::Y"

Ext. to Module• Parents

active_support/core_ext/module/introspection.rb

• parents

module X  module Y    module Z    end  endendM = X::Y::Z X::Y::Z.parents # => [X::Y, X, Object]M.parents       # => [X::Y, X, Object]

Ext. to Module• local_constants

module X  X1 = 1  X2 = 2  module Y    Y1 = :y1    X1 = :overrides_X1_above  endend X.local_constants    # => ["X2", "X1", "Y"], assumes Ruby 1.8X::Y.local_constants # => ["X1", "Y1"], assumes Ruby 1.8

active_support/core_ext/module/introspection.rb

• local_constant_names ⟶ always, strings

as symbols in Ruby 1.9

deprecated!!!

Ext. to Module• const_defined? /_get /_set

Math.const_defined? "PI" #=> trueIO.const_defined? :SYNC #=> trueIO.const_defined? :SYNC, false #=> false

active_support/core_ext/module/introspection.rb

Math.const_get(:PI) #=> 3.14159265358979

Math.const_set("HIGH_SCHOOL_PI", 22.0/7.0) #=> 3.14285714285714Math::HIGH_SCHOOL_PI - Math::PI #=> 0.00126448926734968

standard ruby methods

bare constant names

Ext. to Module• const_defined? /_get /_set

module Foo class Bar VAL = 10 end

class Baz < Bar; endend

Object.const_get 'Foo::Baz::VAL' # => 10Object.const_get 'Foo::Baz::VAL', false # => NameError

active_support/core_ext/module/introspection.rb

standard ruby methods

bare constant names

flag for inherit

Ext. to Module• qualified_const_defined? /_get /_set

module M  X = 1end module N  class C    include M  endend

active_support/core_ext/module/qualified_const.rb

new extended methods

N.qualified_const_defined?("C::X", false) N.qualified_const_defined?("C::X", true)  N.qualified_const_defined?("C::X")       

relative to their receiver

qualified constant names

Ext. to Module• synchronize

class Counter  @@mutex = Mutex.new  attr_reader :value   def initialize    @value = 0  end   def incr    @value += 1 # non-atomic  end  synchronize :incr, :with => '@@mutex'end

active_support/core_ext/module/synchronization.rb

DEPRECATION WARNING: synchronize is deprecated and will be removed from Rails 4.0.

Ext. to Module• reachable?

module Mend M.reachable? # => true

orphan = Object.send(:remove_const, :M) # The module object is orphan now but it still has a name.orphan.name # => "M" # You cannot reach it via the constant M because it does not even exist.orphan.reachable? # => false # Let's define a module called "M" again.module Mend # The constant M exists now again, and it stores a module# object called "M", but it is a new instance.orphan.reachable? # => false

active_support/core_ext/module/reachable.rb

The constant M exists now, and it stores a module object called "M"

Ext. to Module• anonymous?

module MendM.name # => "M" N = Module.newN.name # => "N" Module.new.name # => "" in 1.8, nil in 1.9

M.anonymous? # => false Module.new.anonymous? # => true

m = Object.send(:remove_const, :M) m.reachable? # => falsem.anonymous? # => false

active_support/core_ext/module/anonymous.rb

Ext. to Module• delegate

class User < ActiveRecord::Base  has_one :profileend

class User < ActiveRecord::Base  has_one :profile   def name    profile.name  endend

class User < ActiveRecord::Base  has_one :profile   delegate :name, :to => :profileend

delegate :name, :age, :address, :twitter, :to => :profiledelegate :name, :to => :profile, :allow_nil => truedelegate :street, :to => :address, :prefix => truedelegate :size, :to => :attachment, :prefix => :avatar

active_support/core_ext/module/delegation.rb

Ext. to Module• redefine_method

redefine_method("#{reflection.name}=") do |new_value|  association = association_instance_get(reflection.name)   if association.nil? || association.target != new_value    association = association_proxy_class.new(self, reflection)  end   association.replace(new_value)  association_instance_set(reflection.name, new_value.nil? ? nil : association)end

active_support/core_ext/module/remove_method.rb

ROR Lab.

감사합니다.����������� ������������������