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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. #include <map>
  5.  
  6. template<typename T>
  7. class Base
  8. {
  9. public:    
  10.     //typedef void (T::*PFunc)(void);
  11.     //typedef void (*PHandler)(void*);
  12. 	using PFunc = void (T::*)(void);
  13. 	using PHandler = void(*)(void*);
  14.     using method_map_t = map< string, PHandler >;
  15.  
  16.     static method_map_t& methods( ) {
  17.         static method_map_t* map_of_methods{};
  18.         if( ! map_of_methods ) map_of_methods = new method_map_t;
  19.         return *map_of_methods;
  20.     }
  21.  
  22.     template<PFunc func>
  23.     static void register_method( string name ) {
  24.         methods()[name] = &Handler<func>;
  25.     }
  26.  
  27.     // generic trampoline
  28.     template<PFunc func>
  29.     static void Handler( void* pInstance ) {
  30.         T* f = reinterpret_cast<T*>(pInstance);
  31.         (f ->* func)();
  32.     }
  33. };
  34.  
  35. class Final : Base<Final>
  36. {
  37. public:
  38.     void Foo(){ cout << "got foo" << endl; }
  39.     void Bar(){ cout << "got bar" << endl; }
  40.  
  41.     static void init(){
  42.         // register_method populates a table of "extern C" function pointers.
  43.         register_method<&Final::Foo>( "foo" ); //, static_cast<PHandler>( &Handler<&Final::Foo> ) );
  44.         register_method<&Final::Bar>( "bar" ); //, static_cast<PHandler>( &Handler<&Final::Bar> ) );
  45.     }
  46. };
  47.  
  48. void InvokeFromC(void* inst, string name) {
  49. 	Base<Final>::PHandler h = Base<Final>::methods()[name];
  50. 	(*h)(inst);
  51. }
  52.  
  53. int main() {
  54. 	Final* f = new Final{};
  55. 	f->init();
  56. 	// simulate invoking from C 
  57. 	InvokeFromC( f, "foo" );
  58. 	InvokeFromC( f, "bar" );
  59.  
  60. 	// your code goes here
  61. 	return 0;
  62. }
Success #stdin #stdout 0s 3476KB
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stdin
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Standard input is empty
stdout
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got foo
got bar
https://ideone.com/ZFQb1f
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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