��JFIF��2� /opt/alt/ruby18/share/ri/1.8/system/Singleton/ Current File: //opt/alt/ruby18/share/ri/1.8/system/Singleton/cdesc-Singleton.yaml
--- !ruby/object:RI::ClassDescription 
attributes: []

class_methods: []

comment: 
- !ruby/struct:SM::Flow::P 
  body: The Singleton module implements the Singleton pattern.
- !ruby/struct:SM::Flow::P 
  body: "Usage:"
- !ruby/struct:SM::Flow::VERB 
  body: "   class Klass\n      include Singleton\n      # ...\n   end\n"
- !ruby/object:SM::Flow::LIST 
  contents: 
  - !ruby/struct:SM::Flow::LI 
    label: "*"
    body: this ensures that only one instance of Klass lets call it ``the instance'' can be created.
  - !ruby/struct:SM::Flow::P 
    body: "a,b = Klass.instance, Klass.instance a == b # =&gt; true a.new # NoMethodError - new is private ..."
  - !ruby/struct:SM::Flow::LI 
    label: "*"
    body: ``The instance'' is created at instantiation time, in other words the first call of Klass.instance(), thus
  - !ruby/struct:SM::Flow::VERB 
    body: "  class OtherKlass\n    include Singleton\n    # ...\n  end\n  ObjectSpace.each_object(OtherKlass){} # =&gt; 0.\n"
  - !ruby/struct:SM::Flow::LI 
    label: "*"
    body: This behavior is preserved under inheritance and cloning.
  type: :BULLET
- !ruby/struct:SM::Flow::P 
  body: This is achieved by marking
- !ruby/object:SM::Flow::LIST 
  contents: 
  - !ruby/struct:SM::Flow::LI 
    label: "*"
    body: Klass.new and Klass.allocate - as private
  type: :BULLET
- !ruby/struct:SM::Flow::P 
  body: Providing (or modifying) the class methods
- !ruby/object:SM::Flow::LIST 
  contents: 
  - !ruby/struct:SM::Flow::LI 
    label: "*"
    body: Klass.inherited(sub_klass) and Klass.clone() - to ensure that the Singleton pattern is properly inherited and cloned.
  - !ruby/struct:SM::Flow::LI 
    label: "*"
    body: "Klass.instance() - returning ``the instance''. After a successful self modifying (normally the first) call the method body is a simple:"
  - !ruby/struct:SM::Flow::VERB 
    body: "   def Klass.instance()\n     return @<em>instance</em>\n   end\n"
  - !ruby/struct:SM::Flow::LI 
    label: "*"
    body: Klass._load(str) - calling Klass.instance()
  - !ruby/struct:SM::Flow::LI 
    label: "*"
    body: Klass._instantiate?() - returning ``the instance'' or nil. This hook method puts a second (or nth) thread calling Klass.instance() on a waiting loop. The return value signifies the successful completion or premature termination of the first, or more generally, current &quot;instantiation thread&quot;.
  type: :BULLET
- !ruby/struct:SM::Flow::P 
  body: The instance method of Singleton are
- !ruby/object:SM::Flow::LIST 
  contents: 
  - !ruby/struct:SM::Flow::LI 
    label: "*"
    body: clone and dup - raising TypeErrors to prevent cloning or duping
  - !ruby/struct:SM::Flow::LI 
    label: "*"
    body: _dump(depth) - returning the empty string. Marshalling strips by default all state information, e.g. instance variables and taint state, from ``the instance''. Providing custom _load(str) and _dump(depth) hooks allows the (partially) resurrections of a previous state of ``the instance''.
  type: :BULLET
constants: []

full_name: Singleton
includes: []

instance_methods: 
- !ruby/object:RI::MethodSummary 
  name: _dump
- !ruby/object:RI::MethodSummary 
  name: clone
- !ruby/object:RI::MethodSummary 
  name: dup
name: Singleton
superclass: