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# load the whole ActiveSupportrequire 'active_support'

# load all the core extensionsrequire 'active_support/core_ext'

# load grouped extensions
require 'active_support/core_ext/object'

# Cherry-pickrequire 'active_support/core_ext/object/blank'

nil.blank?#=> true false.blank? #=> true
''.blank?    #=> true
[].blank?    #=> true {}.blank?    #=> true 

# without try
unless @number.nil?
  @number.next
end
 
# with try
@number.try(:next)
# Accepts block too!@person.try { |p| "#{p.first_name} #{p.last_name}" }

active_support/core_ext/object/try.rb

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

silence_warnings { Object.const_set "RAILS_DEFAULT_LOGGER", logger }

silence_stream(STDOUT) do
  # STDOUT is silent here
end

quietly { system 'bundle install' }
# If the user is locked the increment is lost, no big deal.
suppress(ActiveRecord::StaleObjectError) do
  current_user.increment! :visits
end

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

 class User < ActiveRecord::Base
  has_one :profile
 
  delegate :name, to: :profile
end

# Delegate several methodsdelegate :name, :age, :address, :twitter, to: :profile

# Handle the cunning nil!delegate :name, to: :profile, allow_nil: true

# Set prefix ie., address_streetdelegate :street, to: :address, prefix: true

# Custom prefixdelegate :size, to: :attachment, prefix: :avatar

" \n  foo\n\r \t bar \n".squish # => "foo bar"

"Oh dear! Oh dear! I shall be late!".truncate(20)
# => "Oh dear! Oh dear!..."

"Oh dear! Oh dear! I shall be late!".truncate(20, omission: '…')
# => "Oh dear! Oh …"

"production".inquiry.production? # => true
"active".inquiry.inactive?       # => false

<<EOS.indent(2)
def some_method
  some_code
end
EOS
# =>
  def some_method
    some_code
  end
"  foo".indent(2)        # => "    foo"
"foo\n\t\tbar".indent(2) # => "\t\tfoo\n\t\t\t\tbar"
"foo".indent(2, "\t")    # => "\t\tfoo"

"foo\n\nbar".indent(2)            # => "  foo\n\n  bar"
"foo\n\nbar".indent(2, nil, true) # => "  foo\n  \n  bar"

"Fixnum".constantize # => Fixnum
 
module M
  X = 1
end
"M::X".constantize # => 1

1234567890.50.to_s(:currency) 
12345678.to_s(:delimited)                     # => 12,345,678
12345678.to_s(:delimited, delimiter: ".")     # => 12.345.678

123.to_s(:human_size)            # => 123 Bytes
1234.to_s(:human_size)           # => 1.21 KB
12345.to_s(:human_size)          # => 12.1 KB

123.to_s(:human)               # => "123"
1234.to_s(:human)              # => "1.23 Thousand"
12345.to_s(:human)             # => "12.3 Thousand"
1234567.to_s(:human)           # => "1.23 Million"

2.multiple_of?(1) # => true
1.multiple_of?(2) # => false

active_support/core_ext/numeric/formatting.rb

[1, 2, 3].sum # => 6
(1..100).sum  # => 5050

[[1, 2], [2, 3], [3, 4]].sum    # => [1, 2, 2, 3, 3, 4]
%w(foo bar baz).sum             # => "foobarbaz"
{a: 1, b: 2, c: 3}.sum # => [:b, 2, :c, 3, :a, 1]

(1..5).sum {|n| n * 2 } # => 30
[2, 4, 6, 8, 10].sum    # => 30

[].sum(1) {|n| n**3} # => 1

invoices.index_by(&:number)
# => {'2009-032' => <Invoice ...>, '2009-008' => <Invoice ...>, ...}

<% if pages.many? %>
  <%= pagination_links %>
<% end %>

@see_more = videos.many? {|video| video.category == params[:category]}

to_visit << node if visited.exclude?(node)

[1, 2, 3].in_groups_of(2) # => [[1, 2], [3, nil]]

[1, 2, 3, 4].in_groups_of(2) do |a, b|  p "#{a} and #{b}"
end
[1, 2, 3].in_groups_of(2, 0) # => [[1, 2], [3, 0]][1, 2, 3].in_groups_of(2, false) # => [[1, 2], [3]]
(-5..5).to_a.split { |i| i.multiple_of?(4) }
# => [[-5], [-3, -2, -1], [1, 2, 3], [5]]
[0, 1, -5, 1, 1, "foo", "bar"].split(1)
# => [[0], [-5], [], ["foo", "bar"]]

{a: 1, b: 2}.except(:a) # => {:b=>2}

{a: 1, b: 2, c: 3}.slice(:a, :c)
# => {:c=>3, :a=>1}
 
{a: 1, b: 2, c: 3}.slice(:b, :X)
# => {:b=>2} # non-existing keys are ignored

hash = {a: 1, b: 2}
rest = hash.extract!(:a) # => {:a=>1}
hash                     # => {:b=>2}

active_support/core_ext/hash/except.rb
active_support/core_ext/hash/slice.rb

{nil => nil, 1 => 1, a: :a}.transform_keys{ |key| key.to_s.upcase }
# => {"" => nil, "A" => :a, "1" => 1}
{nil => nil, 1 => 1, nested: {a: 3, 5 => 5}}.deep_transform_keys{ |key| key.to_s.upcase }
# => {""=>nil, "1"=>1, "NESTED"=>{"A"=>3, "5"=>5}}'

{nil => nil, 1 => 1, a: :a}.stringify_keys
# => {"" => nil, "a" => :a, "1" => 1}

{nil => nil, 1 => 1, nested: {a: 3, 5 => 5}}.deep_stringify_keys
# => {""=>nil, "1"=>1, "nested"=>{"a"=>3, "5"=>5}}

{nil => nil, 1 => 1, "a" => "a"}.symbolize_keys
# => {1=>1, nil=>nil, :a=>"a"}

{nil => nil, 1 => 1, "nested" => {"a" => 3, 5 => 5}}.deep_symbolize_keys
# => {nil=>nil, 1=>1, nested:{a:3, 5=>5}}

{a: 1}.with_indifferent_access["a"] # => 1
{a: 1, 'b' => 2}.with_indifferent_access[:b] # => 2

• Extensions to Regexp
  
• Extensions to Range
  
• Extensions to Proc
  
• Extensions to Date
  
• Extensions to DateTime
  
• Extensions to Time
  
• Extensions to File
  
• Extensions to Marshal
  
• Extensions to Logger
  
• Extensions to NameError
  
• Extensions to LoadError