JezK
Edit File: singleton.rbs
# <!-- rdoc-file=lib/singleton.rb --> # The Singleton module implements the Singleton pattern. # # ## Usage # # To use Singleton, include the module in your class. # # class Klass # include Singleton # # ... # end # # This ensures that only one instance of Klass can be created. # # a,b = Klass.instance, Klass.instance # # a == b # # => true # # Klass.new # # => NoMethodError - new is private ... # # The instance is created at upon the first call of Klass.instance(). # # class OtherKlass # include Singleton # # ... # end # # ObjectSpace.each_object(OtherKlass){} # # => 0 # # OtherKlass.instance # ObjectSpace.each_object(OtherKlass){} # # => 1 # # This behavior is preserved under inheritance and cloning. # # ## Implementation # # This above is achieved by: # # * Making Klass.new and Klass.allocate private. # # * Overriding Klass.inherited(sub_klass) and Klass.clone() to ensure that the # Singleton properties are kept when inherited and cloned. # # * Providing the Klass.instance() method that returns the same object each # time it is called. # # * Overriding Klass._load(str) to call Klass.instance(). # # * Overriding Klass#clone and Klass#dup to raise TypeErrors to prevent # cloning or duping. # # # ## Singleton and Marshal # # By default Singleton's #_dump(depth) returns the empty string. Marshalling by # default will strip state information, e.g. instance variables from the # instance. Classes using Singleton can provide custom _load(str) and # _dump(depth) methods to retain some of the previous state of the instance. # # require 'singleton' # # class Example # include Singleton # attr_accessor :keep, :strip # def _dump(depth) # # this strips the @strip information from the instance # Marshal.dump(@keep, depth) # end # # def self._load(str) # instance.keep = Marshal.load(str) # instance # end # end # # a = Example.instance # a.keep = "keep this" # a.strip = "get rid of this" # # stored_state = Marshal.dump(a) # # a.keep = nil # a.strip = nil # b = Marshal.load(stored_state) # p a == b # => true # p a.keep # => "keep this" # p a.strip # => nil # module Singleton def self.__init__: (Class klass) -> Class # <!-- # rdoc-file=lib/singleton.rb # - instance() # --> # Returns the singleton instance. # def self.instance: () -> instance public # <!-- # rdoc-file=lib/singleton.rb # - _dump(depth = -1) # --> # By default, do not retain any state when marshalling. # def _dump: (?Integer depth) -> String # <!-- # rdoc-file=lib/singleton.rb # - clone() # --> # Raises a TypeError to prevent cloning. # def clone: () -> bot # <!-- # rdoc-file=lib/singleton.rb # - dup() # --> # Raises a TypeError to prevent duping. # def dup: () -> bot end Singleton::VERSION: String