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  1. #include <iostream>
  2.  
  3. using namespace std;
  4.  
  5. struct AbstractResource {
  6.   int ref_count;
  7.   virtual void do_something() = 0;
  8.   AbstractResource() : ref_count(0) {}
  9.   virtual ~AbstractResource(){}
  10. };
  11.  
  12. struct Resource0 : public AbstractResource {
  13.   void do_something(){
  14.     cout << "Do somthing with Resource0 at " << this << endl;
  15.   }
  16.   Resource0() : AbstractResource() {
  17.     cout << "Created : Resource0 at " << this << endl;
  18.   }
  19.   ~Resource0(){
  20.     cout << "Clean-uped : Resource0 at " << this << endl;
  21.   }
  22. };
  23.  
  24. struct Resource1 : public AbstractResource {
  25.   void do_something(){
  26.     cout << "Do somthing with Resource1 at " << this << endl;
  27.   }
  28.   Resource1() : AbstractResource() {
  29.     cout << "Created : Resource1 at " << this << endl;
  30.   }
  31.   ~Resource1(){
  32.     cout << "Clean-uped : Resource1 at " << this << endl;
  33.   }
  34. };
  35.  
  36. struct Resource {
  37.   AbstractResource *delegatee;
  38.   void do_something() {
  39.     delegatee->do_something();
  40.   }
  41.   Resource(AbstractResource *resource) 
  42.       : delegatee(resource) {
  43.     (delegatee->ref_count)++;
  44.   }
  45.   Resource(const Resource &orig)
  46.       : delegatee(orig.delegatee) {
  47.     (delegatee->ref_count)++;
  48.   }
  49.   Resource &operator=(const Resource &rhs){
  50.     if(delegatee != rhs.delegatee){
  51.       if(--(delegatee->ref_count) <= 0){
  52.         delete delegatee;
  53.       }
  54.       delegatee = rhs.delegatee;
  55.       (delegatee->ref_count)++;
  56.     }
  57.     return *this;
  58.   }
  59.   ~Resource() {
  60.     if(--(delegatee->ref_count) < 1){
  61.       delete delegatee;
  62.     }
  63.   }
  64. };
  65.  
  66. struct ResourceManager {
  67.   static Resource get_resource(const int &type){
  68.     return Resource((type != 0) 
  69.         ? (AbstractResource *)new Resource1() 
  70.         : (AbstractResource *)new Resource0()); 
  71.   }
  72. };
  73.  
  74. int main() {
  75.   Resource r0(ResourceManager::get_resource(0));
  76.   r0.do_something();
  77.  
  78.   Resource r1(ResourceManager::get_resource(1));
  79.   r1.do_something();
  80.  
  81.   {
  82.     Resource r0_copy(r0);
  83.     r0_copy.do_something();
  84.  
  85.     Resource r1_another(ResourceManager::get_resource(1));
  86.     r1_another.do_something();
  87.   }
  88.  
  89.   return 0;
  90. }
  91.  
Success #stdin #stdout 0s 2860KB
comments (?)
stdin 
Standard input is empty
stdout 
Created : Resource0 at 0x9e79008
Do somthing with Resource0 at 0x9e79008
Created : Resource1 at 0x9e79018
Do somthing with Resource1 at 0x9e79018
Do somthing with Resource0 at 0x9e79008
Created : Resource1 at 0x9e79028
Do somthing with Resource1 at 0x9e79028
Clean-uped : Resource1 at 0x9e79028
Clean-uped : Resource1 at 0x9e79018
Clean-uped : Resource0 at 0x9e79008
https://ideone.com/w04wK
language:
C++ (gcc 8.3)
created:
13 years ago
visibility:
public

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