Lists methods unique to a class.

Returns a list of arguments and an options hash. Source taken from RSpec.

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

This simplifies

  if !address.nil? && !address.empty?

to

  if !address.blank?

Defines an instance method within a class

Adds methods to a metaclass

The hidden singleton lurks behind everyone

Lists methods unique to an instance.