Methods

Included Modules

  • Java

Constants

APP_PATH = File.expand_path("test/dummy/config/application", ENGINE_ROOT)

Instance Public methods

acts_like?(duck)

Provides a way to check whether some class acts like some other class based on the existence of an appropriately-named marker method.

A class that provides the same interface as SomeClass may define a marker method named acts_like_some_class? to signal its compatibility to callers of acts_like?(:some_class).

For example, Active Support extends Date to define an acts_like_date? method, and extends Time to define acts_like_time?. As a result, developers can call x.acts_like?(:time) and x.acts_like?(:date) to test duck-type compatibility, and classes that are able to act like Time can also define an acts_like_time? method to interoperate.

Note that the marker method is only expected to exist. It isn’t called, so its body or return value are irrelevant.

Example: A class that provides the same interface as String

This class may define:

class Stringish
  def acts_like_string?
  end
end

Then client code can query for duck-type-safeness this way:

Stringish.new.acts_like?(:string) # => true
πŸ“ Source code
# File activesupport/lib/active_support/core_ext/object/acts_like.rb, line 33
  def acts_like?(duck)
    case duck
    when :time
      respond_to? :acts_like_time?
    when :date
      respond_to? :acts_like_date?
    when :string
      respond_to? :acts_like_string?
    else
      respond_to? :"acts_like_#{duck}?"
    end
  end
πŸ”Ž See on GitHub

blank?()

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

This simplifies

!address || address.empty?

to

address.blank?

@return [true, false]

πŸ“ Source code
# File activesupport/lib/active_support/core_ext/object/blank.rb, line 18
  def blank?
    respond_to?(:empty?) ? !!empty? : !self
  end
πŸ”Ž See on GitHub

deep_dup()

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
πŸ“ Source code
# File activesupport/lib/active_support/core_ext/object/deep_dup.rb, line 15
  def deep_dup
    duplicable? ? dup : self
  end
πŸ”Ž See on GitHub

duplicable?()

Can you safely dup this object?

False for method objects; true otherwise.

πŸ“ Source code
# File activesupport/lib/active_support/core_ext/object/duplicable.rb, line 26
  def duplicable?
    true
  end
πŸ”Ž See on GitHub

html_safe?()

πŸ“ Source code
# File activesupport/lib/active_support/core_ext/string/output_safety.rb, line 7
  def html_safe?
    false
  end
πŸ”Ž See on GitHub

in?(another_object)

Returns true if this object is included in the argument.

When argument is a Range, #cover? is used to properly handle inclusion check within open ranges. Otherwise, argument must be any object which responds to #include?. Usage:

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

For non Range arguments, this will throw an ArgumentError if the argument doesn’t respond to #include?.

πŸ“ Source code
# File activesupport/lib/active_support/core_ext/object/inclusion.rb, line 15
  def in?(another_object)
    case another_object
    when Range
      another_object.cover?(self)
    else
      another_object.include?(self)
    end
  rescue NoMethodError
    raise ArgumentError.new("The parameter passed to #in? must respond to #include?")
  end
πŸ”Ž See on GitHub

instance_values()

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

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

C.new(0, 1).instance_values # => {"x" => 0, "y" => 1}
πŸ“ Source code
# File activesupport/lib/active_support/core_ext/object/instance_variables.rb, line 14
  def instance_values
    instance_variables.to_h do |ivar|
      [ivar[1..-1].freeze, instance_variable_get(ivar)]
    end
  end
πŸ”Ž See on GitHub

instance_variable_names()

Returns an array of instance variable names as strings including β€œ@”.

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

C.new(0, 1).instance_variable_names # => ["@y", "@x"]
πŸ“ Source code
# File activesupport/lib/active_support/core_ext/object/instance_variables.rb, line 30
    def instance_variable_names
      instance_variables.map(&:name)
    end
πŸ”Ž See on GitHub

presence()

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'

becomes

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

@return [Object]

πŸ“ Source code
# File activesupport/lib/active_support/core_ext/object/blank.rb, line 45
  def presence
    self if present?
  end
πŸ”Ž See on GitHub

presence_in(another_object)

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]

πŸ“ Source code
# File activesupport/lib/active_support/core_ext/object/inclusion.rb, line 34
  def presence_in(another_object)
    in?(another_object) ? self : nil
  end
πŸ”Ž See on GitHub

present?()

An object is present if it’s not blank.

@return [true, false]

πŸ“ Source code
# File activesupport/lib/active_support/core_ext/object/blank.rb, line 25
  def present?
    !blank?
  end
πŸ”Ž See on GitHub

to_param()

Alias of to_s.

πŸ“ Source code
# File activesupport/lib/active_support/core_ext/object/to_query.rb, line 7
  def to_param
    to_s
  end
πŸ”Ž See on GitHub

to_query(key)

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

πŸ“ Source code
# File activesupport/lib/active_support/core_ext/object/to_query.rb, line 13
  def to_query(key)
    "#{CGI.escape(key.to_param)}=#{CGI.escape(to_param.to_s)}"
  end
πŸ”Ž See on GitHub

try(*args, &block)

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

@person.try(:name)

instead of

@person.name if @person

try calls can be chained:

@person.try(:spouse).try(:name)

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|
  ...
end

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|
  ...
end

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.

πŸ”Ž See on GitHub

try!(*args, &block)

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
πŸ”Ž See on GitHub

with(**attributes)

Set and restore public attributes around a block.

client.timeout # => 5
client.with(timeout: 1) do
  client.timeout # => 1
end
client.timeout # => 5

This method is a shorthand for the common begin/ensure pattern:

old_value = object.attribute
begin
  object.attribute = new_value
  # do things
ensure
  object.attribute = old_value
end

It can be used on any object as long as both the reader and writer methods are public.

πŸ“ Source code
# File activesupport/lib/active_support/core_ext/object/with.rb, line 24
  def with(**attributes)
    old_values = {}
    begin
      attributes.each do |key, value|
        old_values[key] = public_send(key)
        public_send("#{key}=", value)
      end
      yield
    ensure
      old_values.each do |key, old_value|
        public_send("#{key}=", old_value)
      end
    end
  end
πŸ”Ž See on GitHub

with_options(options, &block)

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 or Hash-like object 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
end

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
  end
end

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
end

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
  end
end

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? }
  end
end

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 }
  end
end

When the block argument is omitted, the decorated Object instance is returned:

module MyStyledHelpers
  def styled
    with_options style: "color: red;"
  end
end

styled.link_to "I'm red", "/"
# => <a href="/" style="color: red;">I'm red</a>

styled.button_tag "I'm red too!"
# => <button style="color: red;">I'm red too!</button>
πŸ“ Source code
# File activesupport/lib/active_support/core_ext/object/with_options.rb, line 92
  def with_options(options, &block)
    option_merger = ActiveSupport::OptionMerger.new(self, options)

    if block
      block.arity.zero? ? option_merger.instance_eval(&block) : block.call(option_merger)
    else
      option_merger
    end
  end
πŸ”Ž See on GitHub