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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. ////////////////////////////////////////////////////////////////////////////////////////
  5.  
  6. template<typename T>
  7. struct Holder {
  8.   Holder() {
  9.     std::cout << "Holder()::Holder()" << std::endl;
  10.     if (!Self)  Self = new T();
  11.     Self->Init();
  12.   }
  13.   ~Holder() {
  14.     if (Self) {
  15.       Self->Cleanup();
  16.       delete Self;
  17.       std::cout << "~Holder()::Holder()" << std::endl;
  18.     }
  19.   }
  20.   T* Self = nullptr;
  21. };
  22.  
  23. ////////////////////////////////////////////////////////////////////////////////////////
  24.  
  25. template <typename T>
  26. class Singleton {
  27.   public:
  28.     static T* Instance() {
  29.       std::cout << "Singlton::Instance()" << std::endl;
  30.       static Holder<T> Dummy;
  31.       return Dummy.Self;
  32.     }
  33.   private:
  34.     Singleton() = delete;
  35.     Singleton(Singleton const&) = delete;
  36.     Singleton& operator= (Singleton const&) = delete;
  37.     Singleton(Singleton const&&) = delete;
  38.     Singleton& operator= (Singleton const&&) = delete;
  39. };
  40.  
  41. class Global {
  42.   public:
  43.     int GetA() { 
  44.       cout << "GetA" << endl;
  45.       return x-1; 
  46.     }
  47.     int GetB() { 
  48.       cout << "GetB" << endl;    	
  49.       return x+1; 
  50.     }
  51.     void Init() {};
  52.     void Cleanup() {};
  53.   private:
  54.     int x = 1;
  55. };
  56.  
  57. struct Test1Class {
  58.   void Print() {
  59.     cout << Singleton<Global>::Instance()->GetA() << endl;  	
  60.   }	
  61. };
  62.  
  63. struct Test2Class {
  64.   void Print() {
  65.     cout << Singleton<Global>::Instance()->GetB() << endl;  	
  66.   }	
  67. };
  68.  
  69.  
  70. int main() {
  71.   Test1Class T1;
  72.   Test2Class T2;
  73.   T1.Print();
  74.   T2.Print();
  75.   return 0;
  76. }
Success #stdin #stdout 0s 15240KB
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stdin
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Standard input is empty
stdout
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Singlton::Instance()
Holder()::Holder()
GetA
0
Singlton::Instance()
GetB
2
~Holder()::Holder()
https://ideone.com/F3urOR
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
public

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