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  1. #include <iostream>
  2. #include <functional>
  3.  
  4. class A{
  5. private:
  6.     int id;
  7. public:
  8.     A(int id) : id(id){};
  9.     void display_id(){ std::cout << "id:" << id << std::endl; }
  10. };
  11.  
  12. class B{
  13. public:
  14.     A *a;
  15.     std::function<void()> f;
  16. public:
  17.     B(A *a): a(a){}
  18.     void set_callback(std::function<void()> f_){
  19.         f = f_;
  20.     }
  21.     void invoke_callback(){
  22.         f();
  23.     }
  24. };
  25.  
  26. int main(){
  27.     A a{5};
  28.     B b{&a};
  29.     // auto f = ;
  30.     b.f = [&](){ std::cout << "hello!" << std::endl; a.display_id(); };
  31.     b.invoke_callback();
  32.  
  33.     return 0;
  34. }
Success #stdin #stdout 0.01s 5292KB
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stdin
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Standard input is empty
stdout
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hello!
id:5
https://ideone.com/8fB9Mw
language:
C++ 4.3.2 (gcc-4.3.2)
created:
7 days ago
visibility:
public

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