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  1. #include <typeinfo>
  2. #include <bitset>
  3. #include <map>
  4. #include <type_traits>
  5.  
  6. class Component {};
  7.  
  8. class ComponentA : public Component {};
  9. class ComponentB : public Component {};
  10. class NonComponent {};
  11.  
  12. constexpr int BITSIZE = 10;
  13.  
  14. class ComponentType {
  15. public: std::bitset<BITSIZE> getBit() { return std::bitset<BITSIZE>(); }
  16. };
  17.  
  18. namespace {
  19.     std::map<std::size_t,ComponentType*> componentTypes;
  20.  
  21.     ComponentType &getTypeFor(const std::type_info &t){
  22.         ComponentType *type = componentTypes[t.hash_code()];
  23.  
  24.         if(!type)
  25.         {
  26.             type = new ComponentType();
  27.             componentTypes[t.hash_code()] = type;
  28.         }
  29.  
  30.         return *type;
  31.  
  32.     };
  33.  
  34.     template<typename T>
  35.     typename std::enable_if<std::is_base_of<Component,T>::value,
  36.                             std::bitset<BITSIZE>>::type
  37.     getBit(const T &t) {
  38.         return getTypeFor(typeid(t)).getBit();
  39.     }
  40.  
  41. }
  42.  
  43. int main() {
  44.     ComponentA a;
  45.     getBit(a);
  46.  
  47.     NonComponent n;
  48.     getBit(n); // error, won't compile
  49. }
Compilation error #stdin compilation error #stdout 0s 0KB
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stdin
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Standard input is empty
compilation info 
prog.cpp: In function 'ComponentType&<unnamed>::getTypeFor(const std::type_info&)':
prog.cpp:22:48: error: 'const class std::type_info' has no member named 'hash_code'
prog.cpp:27:30: error: 'const class std::type_info' has no member named 'hash_code'
prog.cpp: In function 'int main()':
prog.cpp:48:13: error: no matching function for call to 'getBit(NonComponent&)'
stdout
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Standard output is empty
https://ideone.com/sYl1D
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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