Automatic destruction of instances in a single-case mode of C + + design mode (garbage collector)

About C + + Singleton mode m_pinstance point to the space destruction problem, m_pinstance manual destruction is often a headache problem, memory and resource leakage is not uncommon, can have a method, let the instance automatically release.

The workaround is to define an internal garbage collection class and define a static member of this class in Singleton. At the end of the program, the system automatically destructors this static member, at this time, the destructor in this class to deconstruct the singleton instance, you can implement the M_pinstance automatic release.

Attach the test code

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 1  #include  <iostream> 2 using namespace std; 3  4  class Singleton 5 { 6 public: 7     static  Singleton *getinstance ()  8     { 9          if  (m_instance == null) 10          {11             m_Instance =  New singleton ();12             cout< < "get singleton instance success" <<endl;13          }14         return m_Instance;15      }16 17 private:18     singleton () {cout<< "Singleton  construction "<<Endl;} 19     static singleton *m_instance;20 21      // This is important22     class GC //  garbage Collection Class 23      {24     public:25       &NBSP;&NBSP;&NBSP;GC () 26         {27              cout<< "Gc construction" <<endl;28  &NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;}29&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;~GC () 30         {31              cout<< "Gc destruction" <<endl;32              // We can destory all the  Resouce here, eg:db connector, file handle and so on33              if  (m_instance != null) 34              {35                  delete m_Instance;36                  m_Instance = NULL;37                  cout<< " Singleton destruction "<<endl;38                  system ("pause");//Do not pause the program will automatically exit, can not see the output information 39              }40         }41      };42     static gc gc;  //static members of the garbage collection class 43 44 };45 46 singleton Static members of the  *singleton::m_instance = null;47 singleton::gc singleton::gc; //class require external initialization of the class, This is important, otherwise the program run even GC constructs will not enter, talk about automatic destruction 48 int main (int argc, char *argv[]) 49 {50      singleton *singletonobj = singleton::getinstance ();51      return 0;52 }

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Operation Result:

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Automatic destruction of instances in a single-case mode of C + + design mode (garbage collector)