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  1. #include <iostream>
  2.  
  3. struct A{
  4.   typedef void (*callback_type)(void*, int);
  5.   callback_type callback;
  6.   void* user_data;
  7.   void set_callback(callback_type cb, void* ud){
  8.      callback = cb; user_data = ud;
  9.   }
  10.   void invoke(){ callback(user_data, 42); }
  11. };
  12.  
  13. struct B{
  14.   static void cb_foo(void* vself, int data){
  15.     B* self = static_cast<B*>(vself);
  16.     self->foo(data);
  17.   }
  18.   void foo(int data){ std::cout << data * 2 << "\n"; }
  19. };
  20.  
  21. struct C{
  22.   static void cb_bar(void* vself, int data){
  23.     C* self = static_cast<C*>(vself);
  24.     self->bar(data);
  25.   }
  26.   void bar(int data){ std::cout << data / 2 << "\n"; }
  27. };
  28.  
  29. int main(){
  30.   A a;
  31.   B b;
  32.   a.set_callback(&B::cb_foo, &b);
  33.   a.invoke();
  34.   C c;
  35.   a.set_callback(&C::cb_bar, &c);
  36.   a.invoke();
  37. }
  38.  
Success #stdin #stdout 0.01s 2680KB
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https://ideone.com/dprhk
language:
C++ (gcc 8.3)
created:
11 years ago
visibility:
public

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