Singleton Pattern

Singleton is one of the important design pattern in software development

Main objective of this pattern is , to create single instance of the  class  . Lets see how we are achieving that



class singleton
{
 private
   singleton() {}  

public:
  static singleton* CreateInstance() {

     if(!instance )
     {
     instance  = new singleton() ;
      }
   
    return instance  ;
   }

static singleton* instance ;

}


Important things you must know :

 1. Why Constructor is private
     -> So that , other class (outside of this class )  can't create the object .
                   

2. Why we need static function  ie  static singleton* CreateInstance()
   ->  From first point , it is clear ,we can't create object of the class . So, static is the only way we can call function with out creating object of the class

3.  Why member is static
   ->  As it is used inside the static function , It should be static
    just google it , you will get more details about it


Advantage :
 Using this pattern you are maintaining only one instance of this class

Setback :
  1. This object is alive as long as application is alive