Singleton pattern design.

Implementation of designe pattern which can be compared to phoenix singleton with advanced instance life management. More...

Collaboration diagram for Singleton pattern design.:

Classes
class	utilmm::singleton::dummy
	base class for utilmm::singleton::wrapper More...
class	utilmm::singleton::server
	Singleton server. More...
struct	utilmm::singleton::use< Ty >
	Access point to singleton. More...
class	utilmm::singleton::wrapper< Ty >
	Wrapper for singleton instances. More...
Namespaces
namespace	utilmm::singleton
	Singleton manipulation.
Files
file	dummy.hh
	Declaration of utilmm::singleton::dummy.
file	server.hh
	Definition of utilmm::singleton::server.
file	server_fwd.hh
	Forward declaration of utilmm::singleton::server.
file	use.hh
	Declararation of utilmm::singleton::use class.
file	use_fwd.hh
	Forward declaration of utilmm::singleton::use.
file	wrapper.hh
	Declaration of utilmm::singleton::wrapper.
file	wrapper_fwd.hh
	Forward declaration of utilmm::singleton::wrapper.

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Detailed Description

Implementation of designe pattern which can be compared to phoenix singleton with advanced instance life management.

This module includes all the classes used to implement a phoenix singleton pattern design supporting shared libraires.

The phoenix singleton pattern design offers the possibility to have a special class with these properties :

• At any time there's no more thazn one instance of the singleton
• The singleton instance exists if and only if it is needed
• If the singleton instance was destroyed but there are new clients then it is recreated.

This implementation offer also a support for shared libraries using one ingleton server with advanced controller of life time for each instances. This controller is a basic phoenix singleton stored in a shared library.

Accessing to a singleton

To access to a singleton we need to use the utilmm::singleton::use class. This class will offer an acces to singleton instance and will manage the singleton life (it can be seen as a reference counting smart pointer.

For example if one class foo need to access to a singleton of type bar . User can code it asd this :

 #include "utilmm/singleton/use.hh"

 class foo {
 private:
   utilmm::singleton::use<bar> bar_s;
   int value;
   
 public:
  foo():value(0) {}
  explicit foo(int v):value(v) {}
  ~foo() {}

  void send_to_bar() {
    bar_s.instance().send(value);
    // or bar_s->send(value);
  }
 };

Making a class a pure singleton

To define a class singleton as a pure singleton (ie it is impossible to access to it except by utilmm::singleton::use ) one can follow this example :

 #include "utilmm/singleton/wrapper_fwd.hh" 

 class pure_singleton {
 public: 
  // [...] 
 private:
   pure_singleton();
   ~pure_singleton();

  // [...] 

   friend class utilmm::singleton::wrapper<pure_singleton>;
 };

All the structors are defined as private then only firends (ie utilmm::singleton::wrapper) can create and destroy the instance then we have the guarantee that this class is a pure phoenix singleton.