Active Support Core Extensions (1)

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

Active Support
Core Extensions
March 16, 2013

Hyoseong Choi

Active Support

• Ruby on Rails components
• actionmailer
• actionpack
• activerecord
• activesupport ...

Active Support

• Ruby language extensions
• Utility classes
• Other transversal stuff

Core Extensions
Stand-Alone Active Support
require 'active_support'

“blank?” method
Cherry-picking
require 'active_support/core_ext/object/blank'

Grouped Core Extensions
require 'active_support/core_ext/object'

All Core Extensions
require 'active_support/core_ext'

All Active Support
require 'active_support/all'

Core Extensions
Active Support within ROR Application

Default
require 'active_support/all'

Barebone setting with Cherry-pickings
config.active_support.bare = true

Ext. to All Objects
• blank?
‣ nil and false 0 and 0.0

‣ whitespaces : spaces, tabs, newlines
‣ empty arrays and hashes !
blank
‣ empty? true

• present?
active_support/core_ext/object/
‣ !blank? blank.rb

Ext. to All Objects
• presence
host = config[:host].presence || 'localhost'

blank.rb

Ext. to All Objects
• duplicable?
"".duplicable? # => true
false.duplicable? # => false

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

duplicable.rb

Ext. to All Objects
• 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(' ')))
  end
end

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

• try!
active_support/core_ext/object/try.rb

Ext. to All Objects
• singleton_class
nil => NilClass
true => TrueClass
false => FalseClass

active_support/core_ext/kernel/
singleton_class.rb

o us
ym s

Singleton Class?
on as
an cl

• 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.

foobar = [ ]
def foobar.say
“Hello”
end

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

o us
ym s

Singleton Class?
on as
an cl

foobar = Array.new module Foo
def foo
def foobar.size "Hello World!"
"Hello World!" end
end end
foobar.size # => "Hello World!"
foobar.class # => Array foobar = []
bizbat = Array.new foobar.extend(Foo)
bizbat.size # => 0 foobar.singleton_methods # => ["foo"]

foobar = [] foobar = []

class << foobar foobar.instance_eval <<EOT
def foo def foo
"Hello World!" "Hello World!"
end end
end EOT

foobar.singleton_methods # => ["foo"] foobar.singleton_methods # => ["foo"]


o us
ym s

Singleton Class?
on as
an cl

• Practical Uses of Singleton Classes
class Foo
class
def self.one () 1 end
method
class << self
def two () 2 end class
end method

def three () 3 end

self.singleton_methods # => ["two", "one"]
self.class # => Class
self # => Foo
end


Ext. to All Objects
• 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)
  end
end

singleton_class.rb

Ext. to All Objects
• acts_like?(duck) same interface?

def acts_like_string?
end

some_klass.acts_like?(:string)

or ple
f m
e xa acts_like_date? (Date class)
acts_like_time? (Time class)

acts_likes.rb

Ext. to All Objects
• to_param(=> to_s) a value for :id placeholder

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

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

=> The return value should not be escaped!
to_param.rb

Ext. to All Objects
• to_query a value for :id placeholder

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

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

=> escaped!
to_query.rb

Ext. to All Objects
es
ca

•
pe
to_query d

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

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

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

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

to_query.rb

Ext. to All Objects
• 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 => :destroy
end

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
  end
end

with_options.rb

Ext. to All Objects
• 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
interpolation
key

# app/views/home/index.html.erb
<%=t 'greet_username', :user => "Bill", :message => "Goodbye" %>

# config/locales/en.yml
en:
  greet_username: "%{message}, %{user}!"

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

with_options.rb

Ext. to All Objects
• with_options
en:
scope of
  activerecord: i18n
    models:
      user: Dude
    attributes:
      user:
        login: "Handle"
      # will translate User attribute "login" as "Handle"

conﬁg/locales/en.yml

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

with_options.rb

Ext. to All Objects
• Instance Variables
class C
  def initialize(x, y)
    @x, @y = x, y
  end
end

C.new(0, 1).instance_values # => {"x" => 0, "y" => 1}

instance_variable.rb

E
Ext. to All Objects
• Silencing Warnings, Streams, and Exceptions
B OS
E R
$V

silence_warnings { Object.const_set "RAILS_DEFAULT_LOGGER", logger }
si
le
st nc
re in
silence_stream(STDOUT) do am g
s
# STDOUT is silent here
end
su ev
bp en
ro i
ce n
ss
quietly { system 'bundle install' } es
si
ex le
ce nc
pt in
# If the user is locked the increment is lost, no big deal. io g
suppress(ActiveRecord::StaleObjectError) do ns
current_user.increment! :visits
end

reporting.rb

Ext. to All Objects
• in?
1.in?(1,2)          # => true
1.in?([1,2])        # => true
"lo".in?("hello")   # => true
25.in?(30..50)      # => false
1.in?(1)            # => ArgumentError

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

inclusion.rb

Active Support Core Extensions (1)

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