Singleton pattern. There is criticism of the use of the singleton pattern, as some consider it an anti-pattern, judging that it is overused, introduces unnecessary restrictions in situations where a sole instance of a class is not actually required, and introduces global state into an application.[1][2][3][4][5][6] In C++ it also serves to isolate from the unpredictability of the order of dynamic initialization, returning control to the programmer.
Common uses[edit] The Abstract Factory, Builder, and Prototype patterns can use Singletons in their implementation.Facade Objects are often Singletons because only one Facade object is required.State objects are often Singletons.Singletons are often preferred to global variables because: They do not pollute the global namespace (or, in languages with namespaces, their containing namespace) with unnecessary variables.[7]They permit lazy allocation and initialization, whereas global variables in many languages will always consume resources.
UML[edit] Reference - C++ singleton GetInstance() return. C++ - Singleton instance declared as static variable of GetInstance method. Singleton Pattern & its implementation with C++ Introduction Suppose we have to use a single object of a class throughout the lifetime of an application.
In C++, it is possible to declare a global object, which can be used anywhere inside the program.