/Ruby on Rails 5.1

class Object

Included modules:



Public Instance Methods

acts_like?(duck) Show source

A duck-type assistant method. For example, Active Support extends Date to define an acts_like_date? method, and extends Time to define acts_like_time?. As a result, we can do x.acts_like?(:time) and x.acts_like?(:date) to do duck-type-safe comparisons, since classes that we want to act like Time simply need to define an acts_like_time? method.

# File activesupport/lib/active_support/core_ext/object/acts_like.rb, line 7
def acts_like?(duck)
  respond_to? :"acts_like_#{duck}?"
blank?() Show source

An object is blank if it's false, empty, or a whitespace string. For example, false, '', ' ', nil, [], and {} are all blank.

This simplifies

!address || address.empty?



@return [true, false]

# File activesupport/lib/active_support/core_ext/object/blank.rb, line 16
def blank?
  respond_to?(:empty?) ? !!empty? : !self
create_fixtures(*fixture_set_names, &block) Show source
# File railties/lib/rails/test_help.rb, line 31
def create_fixtures(*fixture_set_names, &block)
  FixtureSet.create_fixtures(ActiveSupport::TestCase.fixture_path, fixture_set_names, {}, &block)
deep_dup() Show source

Returns a deep copy of object if it's duplicable. If it's not duplicable, returns self.

object = Object.new
dup    = object.deep_dup
dup.instance_variable_set(:@a, 1)

object.instance_variable_defined?(:@a) # => false
dup.instance_variable_defined?(:@a)    # => true
# File activesupport/lib/active_support/core_ext/object/deep_dup.rb, line 13
def deep_dup
  duplicable? ? dup : self
duplicable?() Show source

Can you safely dup this object?

False for method objects; true otherwise.

# File activesupport/lib/active_support/core_ext/object/duplicable.rb, line 24
def duplicable?
html_safe?() Show source
# File activesupport/lib/active_support/core_ext/string/output_safety.rb, line 124
def html_safe?
in?(another_object) Show source

Returns true if this object is included in the argument. Argument must be any object which responds to #include?. Usage:

characters = ["Konata", "Kagami", "Tsukasa"]
"Konata".in?(characters) # => true

This will throw an ArgumentError if the argument doesn't respond to #include?.

# File activesupport/lib/active_support/core_ext/object/inclusion.rb, line 10
def in?(another_object)
rescue NoMethodError
  raise ArgumentError.new("The parameter passed to #in? must respond to #include?")
instance_values() Show source

Returns a hash with string keys that maps instance variable names without “@” to their corresponding values.

class C
  def initialize(x, y)
    @x, @y = x, y

C.new(0, 1).instance_values # => {"x" => 0, "y" => 1}
# File activesupport/lib/active_support/core_ext/object/instance_variables.rb, line 12
def instance_values
  Hash[instance_variables.map { |name| [name[1..-1], instance_variable_get(name)] }]
instance_variable_names() Show source

Returns an array of instance variable names as strings including “@”.

class C
  def initialize(x, y)
    @x, @y = x, y

C.new(0, 1).instance_variable_names # => ["@y", "@x"]
# File activesupport/lib/active_support/core_ext/object/instance_variables.rb, line 25
def instance_variable_names
presence() Show source

Returns the receiver if it's present otherwise returns nil. object.presence is equivalent to

object.present? ? object : nil

For example, something like

state   = params[:state]   if params[:state].present?
country = params[:country] if params[:country].present?
region  = state || country || 'US'


region = params[:state].presence || params[:country].presence || 'US'

@return [Object]

# File activesupport/lib/active_support/core_ext/object/blank.rb, line 43
def presence
  self if present?
presence_in(another_object) Show source

Returns the receiver if it's included in the argument otherwise returns nil. Argument must be any object which responds to #include?. Usage:

params[:bucket_type].presence_in %w( project calendar )

This will throw an ArgumentError if the argument doesn't respond to #include?.

@return [Object]

# File activesupport/lib/active_support/core_ext/object/inclusion.rb, line 24
def presence_in(another_object)
  in?(another_object) ? self : nil
present?() Show source

An object is present if it's not blank.

@return [true, false]

# File activesupport/lib/active_support/core_ext/object/blank.rb, line 23
def present?
to_param() Show source

Alias of to_s.

# File activesupport/lib/active_support/core_ext/object/to_query.rb, line 5
def to_param
to_query(key) Show source

Converts an object into a string suitable for use as a URL query string, using the given key as the param name.

# File activesupport/lib/active_support/core_ext/object/to_query.rb, line 11
def to_query(key)
try(*a, &b) Show source

Invokes the public method whose name goes as first argument just like public_send does, except that if the receiver does not respond to it the call returns nil rather than raising an exception.

This method is defined to be able to write


instead of

@person.name if @person

try calls can be chained:


instead of

@person.spouse.name if @person && @person.spouse

try will also return nil if the receiver does not respond to the method:

@person.try(:non_existing_method) # => nil

instead of

@person.non_existing_method if @person.respond_to?(:non_existing_method) # => nil

try returns nil when called on nil regardless of whether it responds to the method:

nil.try(:to_i) # => nil, rather than 0

Arguments and blocks are forwarded to the method if invoked:

@posts.try(:each_slice, 2) do |a, b|

The number of arguments in the signature must match. If the object responds to the method the call is attempted and ArgumentError is still raised in case of argument mismatch.

If try is called without arguments it yields the receiver to a given block unless it is nil:

@person.try do |p|

You can also call try with a block without accepting an argument, and the block will be instance_eval'ed instead:

@person.try { upcase.truncate(50) }

Please also note that try is defined on Object. Therefore, it won't work with instances of classes that do not have Object among their ancestors, like direct subclasses of BasicObject.

# File activesupport/lib/active_support/core_ext/object/try.rb, line 91
try!(*a, &b) Show source

Same as try, but raises a NoMethodError exception if the receiver is not nil and does not implement the tried method.

"a".try!(:upcase) # => "A"
nil.try!(:upcase) # => nil
123.try!(:upcase) # => NoMethodError: undefined method `upcase' for 123:Integer
# File activesupport/lib/active_support/core_ext/object/try.rb, line 103
unescape(str, escaped = /%[a-fA-F\d]{2}/) Show source
# File activesupport/lib/active_support/core_ext/uri.rb, line 8
def unescape(str, escaped = /%[a-fA-F\d]{2}/)
  # TODO: Are we actually sure that ASCII == UTF-8?
  # YK: My initial experiments say yes, but let's be sure please
  enc = str.encoding
  enc = Encoding::UTF_8 if enc == Encoding::US_ASCII
  str.gsub(escaped) { |match| [match[1, 2].hex].pack("C") }.force_encoding(enc)
with_options(options, &block) Show source

An elegant way to factor duplication out of options passed to a series of method calls. Each method called in the block, with the block variable as the receiver, will have its options merged with the default options hash provided. Each method called on the block variable must take an options hash as its final argument.

Without with_options, this code contains duplication:

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

Using with_options, we can remove the duplication:

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

It can also be used with an explicit receiver:

I18n.with_options locale: user.locale, scope: 'newsletter' do |i18n|
  subject i18n.t :subject
  body    i18n.t :body, user_name: user.name

When you don't pass an explicit receiver, it executes the whole block in merging options context:

class Account < ActiveRecord::Base
  with_options dependent: :destroy do
    has_many :customers
    has_many :products
    has_many :invoices
    has_many :expenses

with_options can also be nested since the call is forwarded to its receiver.

NOTE: Each nesting level will merge inherited defaults in addition to their own.

class Post < ActiveRecord::Base
  with_options if: :persisted?, length: { minimum: 50 } do
    validates :content, if: -> { content.present? }

The code is equivalent to:

validates :content, length: { minimum: 50 }, if: -> { content.present? }

Hence the inherited default for `if` key is ignored.

NOTE: You cannot call class methods implicitly inside of with_options. You can access these methods using the class name instead:

class Phone < ActiveRecord::Base
  enum phone_number_type: [home: 0, office: 1, mobile: 2]

  with_options presence: true do
    validates :phone_number_type, inclusion: { in: Phone.phone_number_types.keys }
# File activesupport/lib/active_support/core_ext/object/with_options.rb, line 76
def with_options(options, &block)
  option_merger = ActiveSupport::OptionMerger.new(self, options)
  block.arity.zero? ? option_merger.instance_eval(&block) : block.call(option_merger)

© 2004–2017 David Heinemeier Hansson
Licensed under the MIT License.