D7net
Home
Console
Upload
information
Create File
Create Folder
About
Tools
:
/
proc
/
self
/
root
/
opt
/
alt
/
ruby34
/
share
/
ri
/
system
/
Singleton
/
Filename :
cdesc-Singleton.ri
back
Copy
U:RDoc::NormalModule[iI"Singleton:ET@0o:RDoc::Markup::Document: @parts[o;;[ o: RDoc::Markup::Paragraph;[I";The Singleton module implements the Singleton pattern.;To: RDoc::Markup::BlankLine S:RDoc::Markup::Heading: leveli: textI" Usage;T@o; ;[I"8To use Singleton, include the module in your class.;T@o:RDoc::Markup::Verbatim;[ I"class Klass ;TI" include Singleton ;TI" # ... ;TI" end ;T: @format0o; ;[I"AThis ensures that only one instance of Klass can be created.;T@o;;[ I"*a,b = Klass.instance, Klass.instance ;TI" ;TI" a == b ;TI"# => true ;TI" ;TI"Klass.new ;TI"-# => NoMethodError - new is private ... ;T;0o; ;[I"HThe instance is created at upon the first call of Klass.instance().;T@o;;[I"class OtherKlass ;TI" include Singleton ;TI" # ... ;TI" end ;TI" ;TI"+ObjectSpace.each_object(OtherKlass){} ;TI" # => 0 ;TI" ;TI"OtherKlass.instance ;TI"+ObjectSpace.each_object(OtherKlass){} ;TI" # => 1 ;T;0o; ;[I">This behavior is preserved under inheritance and cloning.;T@S; ; i; I"Implementation;T@o; ;[I" This above is achieved by:;T@o:RDoc::Markup::List: @type: BULLET: @items[ o:RDoc::Markup::ListItem: @label0;[o; ;[I"1Making Klass.new and Klass.allocate private.;T@o;;0;[o; ;[I"POverriding Klass.inherited(sub_klass) and Klass.clone() to ensure that the ;TI"=Singleton properties are kept when inherited and cloned.;T@o;;0;[o; ;[I"MProviding the Klass.instance() method that returns the same object each ;TI"time it is called.;T@o;;0;[o; ;[I":Overriding Klass._load(str) to call Klass.instance().;T@o;;0;[o; ;[I"IOverriding Klass#clone and Klass#dup to raise TypeErrors to prevent ;TI"cloning or duping.;T@S; ; i; I"Singleton and Marshal;T@o; ;[ I"SBy default Singleton's #_dump(depth) returns the empty string. Marshalling by ;TI"Vdefault will strip state information, e.g. instance variables from the instance. ;TI"TClasses using Singleton can provide custom _load(str) and _dump(depth) methods ;TI":to retain some of the previous state of the instance.;T@o;;[!I"require 'singleton' ;TI" ;TI"class Example ;TI" include Singleton ;TI"# attr_accessor :keep, :strip ;TI" def _dump(depth) ;TI"@ # this strips the @strip information from the instance ;TI"$ Marshal.dump(@keep, depth) ;TI" end ;TI" ;TI" def self._load(str) ;TI"+ instance.keep = Marshal.load(str) ;TI" instance ;TI" end ;TI" end ;TI" ;TI"a = Example.instance ;TI"a.keep = "keep this" ;TI"!a.strip = "get rid of this" ;TI" ;TI"$stored_state = Marshal.dump(a) ;TI" ;TI"a.keep = nil ;TI"a.strip = nil ;TI"$b = Marshal.load(stored_state) ;TI"p a == b # => true ;TI"!p a.keep # => "keep this" ;TI"p a.strip # => nil;T;0: @fileI"lib/singleton.rb;T:0@omit_headings_from_table_of_contents_below0;0;0[ [U:RDoc::Constant[i I" VERSION;TI"Singleton::VERSION;T: public0o;;[ ;@~;0@~@cRDoc::NormalModule0[[I" SingletonInstanceMethods;To;;[ ;@~;0I"lib/singleton.rb;T[[I" class;T[[;[[I" _load;T@�[I" instance;T@�[I" module_with_class_methods;T@�[:protected[ [: private[ [I" instance;T[[;[ [;[ [;[ [[I" SingletonClassProperties;To;;[ ;@~;0@�[U:RDoc::Context::Section[i 0o;;[ ;0;0[@~@~cRDoc::TopLevel