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  1. #include <iostream>
  2. #include <vector>
  3.  
  4. class VisualizableVector {
  5.   public:
  6.     class proxy {
  7.       public:
  8.         proxy (std::vector<int> *v) : vect (v) {
  9.             std::cout << "Before size is: " << vect->size() << std::endl;
  10.         }
  11.         std::vector<int> * operator -> () { return vect; }
  12.         std::vector<int> & operator * () { return *vect; }
  13.         operator std::vector<int>&() { return *vect; }
  14.         ~proxy () { std::cout << "After size is: " << vect->size() << std::endl; }
  15.       private:
  16.         std::vector <int> * vect;
  17.     };        
  18.     VisualizableVector (std::vector<int> *v) : vect(v) {}            
  19.     ~VisualizableVector () { delete vect; }   
  20.     proxy operator -> () { return proxy (vect); }
  21.     proxy operator * () { return proxy (vect); }
  22.   private:
  23.     std::vector <int> * vect;
  24. };
  25.  
  26. int main()
  27. {
  28.   VisualizableVector vecc (new std::vector<int>);
  29.  
  30.   vecc->push_back (10);         // 1. Note use of -> operator instead of . operator      
  31.   vecc->push_back (20);         // 2. ok      
  32.   (*vecc)->push_back (30);      // 3. ok      
  33.   //(*vecc).push_back (40);    	// 4. error
  34.   static_cast<std::vector<int>>(*vecc).push_back (40); // 4.a ok
  35.  
  36.   std::vector<int>& vec_ref = *vecc;	// implicit static_cast<std::vector<int>>
  37.   vec_ref.push_back (40);		// 4.b ok
  38.  
  39.   (**vecc).push_back (50);      // 5. ok      
  40.   // vecc->->push_back (60);    // 6. error     
  41. }
Success #stdin #stdout 0s 3464KB
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stdin
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Standard input is empty
stdout
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Before size is: 0
After size is: 1
Before size is: 1
After size is: 2
Before size is: 2
After size is: 3
Before size is: 3
After size is: 3
Before size is: 3
After size is: 3
Before size is: 4
After size is: 5
https://ideone.com/IlvhPc
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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