Active SupportCore Extensions

ROR lab. DD-1- The 1st round -

March 16, 2013

Hyoseong Choi

• Ruby on Rails components

• actionmailer

• actionpack

• activerecord

• activesupport ...

Active Support

• Ruby on Rails components

• actionmailer

• actionpack

• activerecord

• activesupport ...

Active Support

Active Support

• Ruby language extensions

• Utility classes

• Other transversal stuff

Core ExtensionsStand-Alone Active Support

require 'active_support'

“blank?” method

Grouped Core Extensionsrequire 'active_support/core_ext/object'

All Core Extensionsrequire 'active_support/core_ext'

All Active Supportrequire 'active_support/all'

require 'active_support/core_ext/object/blank'

Cherry-picking

Core ExtensionsActive Support within ROR Application

require 'active_support/all'

Default

config.active_support.bare = true

Barebone setting with Cherry-pickings

Ext. to All Objects• blank?

‣ nil and false

‣ whitespaces : spaces, tabs, newlines

‣ empty arrays and hashes

‣ empty? true

• present?

‣ !blank?

0 and 0.0

!blank

active_support/core_ext/object/blank.rb

Ext. to All Objects• presence

host = config[:host].presence || 'localhost'

active_support/core_ext/object/blank.rb

Ext. to All Objects

active_support/core_ext/object/duplicable.rb

• duplicable?

"".duplicable?     # => truefalse.duplicable?  # => false

Singletons : nil, false, true, symobls, numbers, and class and module objects

Ext. to All Objects

active_support/core_ext/object/try.rb

• try

def log_info(sql, name, ms)  if @logger.try(:debug?)    name = '%s (%.1fms)' % [name || 'SQL', ms]    @logger.debug(format_log_entry(name, sql.squeeze(' ')))  endend

@person.try { |p| "#{p.first_name} #{p.last_name}" }

• try!

Ext. to All Objects

active_support/core_ext/kernel/singleton_class.rb

• singleton_class

nil => NilClasstrue => TrueClassfalse => FalseClass

Singleton Class?• When you add a method to a specific object, Ruby inserts

a new anonymous class into the inheritance hierarchy as a container to hold these types of methods.

http://www.devalot.com/articles/2008/09/ruby-singleton

anonymous

class

foobar = [ ]def foobar.say “Hello”end

Singleton Class?

http://www.devalot.com/articles/2008/09/ruby-singleton

anonymous

class

module Foo def foo "Hello World!" endend

foobar = []foobar.extend(Foo)foobar.singleton_methods # => ["foo"]

foobar = []

class << foobar def foo "Hello World!" endend

foobar.singleton_methods # => ["foo"]

foobar = []

foobar.instance_eval <<EOT def foo "Hello World!" endEOT foobar.singleton_methods # => ["foo"]

foobar = Array.new

def foobar.size "Hello World!"endfoobar.size # => "Hello World!"foobar.class # => Arraybizbat = Array.newbizbat.size # => 0

Singleton Class?

http://www.devalot.com/articles/2008/09/ruby-singleton

class Foo def self.one () 1 end class << self def two () 2 end end

def three () 3 end self.singleton_methods # => ["two", "one"] self.class # => Class self # => Fooend

• Practical Uses of Singleton Classes

classmethod

classmethod

anonymous

class

Ext. to All Objects

active_support/core_ext/kernel/singleton_class.rb

• class_eval(*args, &block)

class Proc  def bind(object)    block, time = self, Time.now    object.class_eval do      method_name = "__bind_#{time.to_i}_#{time.usec}"      define_method(method_name, &block)      method = instance_method(method_name)      remove_method(method_name)      method    end.bind(object)  endend

Ext. to All Objects

active_support/core_ext/object/acts_likes.rb

• acts_like?(duck)

some_klass.acts_like?(:string)

same interface?

def acts_like_string?end

acts_like_date? (Date class)acts_like_time? (Time class)

for

example

Ext. to All Objects

active_support/core_ext/object/to_param.rb

• to_param(=> to_s) a value for :id placeholder

class User  def to_param    "#{id}-#{name.parameterize}"  endend

user_path(@user) # => "/users/357-john-smith"➧

=> The return value should not be escaped!

overwriting

Ext. to All Objects

active_support/core_ext/object/to_query.rb

• to_query a value for :id placeholder

class User  def to_param    "#{id}-#{name.parameterize}"  endend

current_user.to_query('user') # => user=357-john-smith➧

=> escaped!

Ext. to All Objects

active_support/core_ext/object/to_query.rb

• to_queryescaped

account.to_query('company[name]')# => "company%5Bname%5D=Johnson+%26+Johnson"

{:c => 3, :b => 2, :a => 1}.to_query # => "a=1&b=2&c=3"

[3.4, -45.6].to_query('sample')# => "sample%5B%5D=3.4&sample%5B%5D=-45.6"

{:id => 89, :name => "John Smith"}.to_query('user')# => "user%5Bid%5D=89&user%5Bname%5D=John+Smith"

Ext. to All Objects

active_support/core_ext/object/with_options.rb

• with_options

class Account < ActiveRecord::Base  has_many :customers, :dependent => :destroy  has_many :products,  :dependent => :destroy  has_many :invoices,  :dependent => :destroy  has_many :expenses,  :dependent => :destroyend

class Account < ActiveRecord::Base  with_options :dependent => :destroy do |assoc|    assoc.has_many :customers    assoc.has_many :products    assoc.has_many :invoices    assoc.has_many :expenses  endend

Ext. to All Objects

active_support/core_ext/object/with_options.rb

• with_options

I18n.with_options locale: user.locale, scope: "newsletter" do |i18n|  subject i18n.t(:subject)  body    i18n.t(:body, user_name: user.name)end

# app/views/home/index.html.erb<%=t 'greet_username', :user => "Bill", :message => "Goodbye" %> # config/locales/en.ymlen:  greet_username: "%{message}, %{user}!"

http://guides.rubyonrails.org/i18n.html

interpolation key

Ext. to All Objects

active_support/core_ext/object/with_options.rb

• with_options

en:  activerecord:    models:      user: Dude    attributes:      user:        login: "Handle"      # will translate User attribute "login" as "Handle"

http://guides.rubyonrails.org/i18n.html

scope ofi18n

config/locales/en.yml

Ext. to All Objects

active_support/core_ext/object/instance_variable.rb

• Instance Variables

class C  def initialize(x, y)    @x, @y = x, y  endend C.new(0, 1).instance_values # => {"x" => 0, "y" => 1}

Ext. to All Objects

active_support/core_ext/kernel/reporting.rb

• Silencing Warnings, Streams, and Exceptions

silence_warnings { Object.const_set "RAILS_DEFAULT_LOGGER", logger }

silence_stream(STDOUT) do  # STDOUT is silent hereend

quietly { system 'bundle install' }

# If the user is locked the increment is lost, no big deal.suppress(ActiveRecord::StaleObjectError) do  current_user.increment! :visitsend

$VERBOSE

even in

subprocessessilencing

exceptions

silencingstreams

Ext. to All Objects

active_support/core_ext/object/inclusion.rb

• in?1.in?(1,2)          # => true1.in?([1,2])        # => true"lo".in?("hello")   # => true25.in?(30..50)      # => false1.in?(1)            # => ArgumentError

[1,2].include? 1         # => true"hello".include? "lo"    # => true(30..50).include? 25     # => false

• include? (array method)

ROR Lab.

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