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  1. #include <iostream>
  2. #include <memory>
  3. using namespace std;
  4.  
  5. class B; // <=== forward declare
  6. class C : public std::enable_shared_from_this<C> {  // inherit publicly 
  7. public:
  8.   virtual B mymethod()  =0;
  9.   virtual ~C() {}    // Attention:  polymorphic class needs virtual destructor
  10. };
  11.  
  12. class A : public C {
  13. public:
  14.   B mymethod()  override;
  15. //private:
  16.   int myvar;
  17. };
  18.  
  19. struct B {
  20.   std::shared_ptr<C> pointer;
  21. };
  22.  
  23. B A::mymethod()  {
  24.   B instance;
  25.   //instance.pointer = std::shared_ptr<A>(this);   //<===== no longer 
  26.   instance.pointer = shared_from_this();  //<===== RETURN A POINTER TO SELF
  27.   return instance;
  28. }
  29. int main() {
  30.   shared_ptr<C> pobject(new A);
  31.   dynamic_pointer_cast<A>(pobject)->myvar=27; // just for verification
  32.   B instance = pobject->mymethod();
  33.   //std::cout << instance.pointer->myvar;   //DOESN'T COMPILE: CANNOT DUMP !!
  34.   std::cout << dynamic_pointer_cast<A>(instance.pointer)->myvar<<endl;
  35.   cout<< instance.pointer.use_count()<<endl;
  36. 	return 0;
  37. }
Success #stdin #stdout 0s 3460KB
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27
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https://ideone.com/rO5o2J
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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