class Object

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

This simplifies

!address || address.empty?

to

address.blank?

@return [true, false]

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

Can you safely dup this object?

False for method objects; true otherwise.

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?.

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
  end
end

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

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

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

C.new(0, 1).instance_variable_names # => ["@y", "@x"]

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]

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]

An object is present if it’s not blank.

@return [true, false]

Set and restore public attributes around a block.

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

The receiver is yielded to the provided block.

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.

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>