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  1. #include <iostream>
  2. #include <type_traits>
  3.  
  4. #define CREATE_CLALLER( cls, method ) \
  5.     struct method { \
  6.         void operator()( cls* obj ) { \
  7.             obj->method(); \
  8.         } \
  9.     }
  10.  
  11. // classes
  12. struct Base {
  13.     void BaseMethod1(){ std::cout << __PRETTY_FUNCTION__ << std::endl; }
  14.     void BaseMethod2(){ std::cout << __PRETTY_FUNCTION__ << std::endl; }
  15.     void BaseMethod3(){ std::cout << __PRETTY_FUNCTION__ << std::endl; }
  16. };
  17. CREATE_CLALLER( Base, BaseMethod1 );
  18. CREATE_CLALLER( Base, BaseMethod2 );
  19. CREATE_CLALLER( Base, BaseMethod3 );
  20.  
  21. struct A final : Base {
  22.      void A_Specific_Operations(){ std::cout << __PRETTY_FUNCTION__ << std::endl; }
  23.      void doSomething();
  24. };
  25. CREATE_CLALLER( A, A_Specific_Operations );
  26.  
  27. struct B final : Base {
  28.      void B_Specific_Operations(){ std::cout << __PRETTY_FUNCTION__ << std::endl; }
  29.      void doSomething();
  30. };
  31. CREATE_CLALLER( B, B_Specific_Operations );
  32.  
  33. /// utilities
  34. struct a_tag { };
  35. struct b_tag { };
  36.  
  37. template < typename... Strategy > 
  38. struct strategy_list { };
  39.  
  40. template < typename Target, typename First, typename... Last >
  41. void execute_strategies( Target* target, strategy_list<First,Last...> ) {
  42.     First()( target );
  43.     execute_strategies( target, strategy_list<Last...>() );
  44. }
  45.  
  46. template < typename Target >
  47. void execute_strategies( Target* target, strategy_list<> ) { }
  48.  
  49. template < typename Tag >
  50. using make_steps = strategy_list<
  51.     BaseMethod1
  52.     , typename std::conditional< 
  53.         !std::is_same<Tag,b_tag>::value
  54.         , BaseMethod2
  55.         , B_Specific_Operations
  56.       >::type
  57.     , typename std::conditional< 
  58.         !std::is_same<Tag,a_tag>::value
  59.         , BaseMethod2
  60.         , A_Specific_Operations
  61.       >::type
  62.     , BaseMethod3
  63. >;
  64.  
  65. // implement codes
  66. void A::doSomething() {
  67.     execute_strategies( this, make_steps<a_tag>() );
  68. }
  69.  
  70. void B::doSomething() {
  71.     execute_strategies( this, make_steps<b_tag>() );
  72. }
  73.  
  74. int main() {
  75.  
  76.     using namespace std;
  77.  
  78.     A().doSomething();
  79.     cout << endl;
  80.     B().doSomething();
  81. }
Success #stdin #stdout 0s 2852KB
comments (?)
stdin 
Standard input is empty
stdout 
void Base::BaseMethod1()
void Base::BaseMethod2()
void A::A_Specific_Operations()
void Base::BaseMethod3()

void Base::BaseMethod1()
void B::B_Specific_Operations()
void Base::BaseMethod2()
void Base::BaseMethod3()
https://ideone.com/g5hKBS
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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