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  1. #include <iostream>
  2. #include <string>
  3. #include <functional>
  4. #include <memory>
  5.  
  6. class MyClass
  7. {
  8.     float myFloat;
  9. public:
  10.     MyClass(float f):myFloat(f){}
  11.  
  12.     void myFunc(int arg1)
  13.     {
  14.         std::cout << arg1 << ", " << myFloat << '\n';
  15.     }
  16. };
  17.  
  18. class MyContainer
  19. {
  20. public:
  21.     MyClass* object;
  22. };
  23.  
  24. // DelayedCaller implementation
  25. class DelayedCaller
  26. {
  27. public:
  28.     template <typename TFunction, typename... TArgs>
  29.     static std::shared_ptr<DelayedCaller> setup(TFunction&& a_func,
  30.                                                 TArgs&&... a_args)
  31.     {
  32.         return std::shared_ptr<DelayedCaller>(new DelayedCaller(
  33.             std::bind(std::forward<TFunction>(a_func),
  34.                       std::forward<TArgs>(a_args)...)));
  35.     }
  36.     void call() const { func_(); }
  37.  
  38. private:
  39.     using func_type = std::function<void()>;
  40.     DelayedCaller(func_type&& a_ft) : func_(std::forward<func_type>(a_ft)) {}
  41.     func_type func_;
  42. };
  43.  
  44. int main()
  45. {
  46.     MyContainer container;
  47.     MyClass c1(45.6);
  48.     container.object = &c1;
  49.     // the next line is the critical one. Instead of myFunc being called
  50.     // on the current value of container.object, it should be called on
  51.     // the one container.object is holding when caller is called.
  52.     auto caller(DelayedCaller::setup(&MyClass::myFunc, std::ref(container.object), 123));
  53.  
  54.     caller->call();
  55.  
  56.     MyClass c2(22.8);
  57.     container.object = &c2;
  58.     caller->call();
  59. }
Success #stdin #stdout 0s 4288KB
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Standard input is empty
stdout
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123, 45.6
123, 22.8
https://ideone.com/8JlmLY
language:
C++ (gcc 8.3)
created:
8 years ago
visibility:
public

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