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  1. #include <iostream>
  2. #include <type_traits>
  3.  
  4. using namespace std;
  5.  
  6.  
  7. #define DETECTED_MEMBER(member_name)                                                      \
  8. template<typename C, typename T>class has_##member_name                                   \
  9. {                                                                                         \
  10.     template<class U> static constexpr auto Check(U*) -> typename                         \
  11.     std::is_same< decltype( std::declval<U>().member_name), T >::type;                    \
  12.                                                                                           \
  13.     template<typename> static constexpr std::false_type Check(...);                       \
  14.     typedef decltype(Check<C>(0)) Result;                                                 \
  15. public:                                                                                   \
  16.     enum { eIS_NOCONST = 0 };                                                             \
  17.     enum { eIS_CONST   = 0 };                                                             \
  18.     enum { eIS_AVAILABLE = Result::value };                                               \
  19. };                                                                                        \
  20. template<class C,typename R, typename... Args>class has_##member_name<C, R(Args...)>      \
  21. {                                                                                         \
  22.     typedef R(C::*Method)(Args...);    typedef R(C::*CMethod)(Args...)const;              \
  23.     template <class U> using NoConst = decltype(static_cast<Method> (&U::member_name));   \
  24.     template <class U> using Const   = decltype(static_cast<CMethod>(&U::member_name));   \
  25.                                                                                           \
  26.     template<class U> static constexpr std::true_type  CheckNoConst( NoConst<U>*p );      \
  27.     template<class>   static constexpr std::false_type CheckNoConst(...);                 \
  28.     typedef decltype(CheckNoConst<C>(0)) NoConstResult;                                   \
  29.                                                                                           \
  30.     template<class U> static constexpr std::true_type  CheckConst( Const<U>*p);           \
  31.     template<class>   static constexpr std::false_type CheckConst(...);                   \
  32.     typedef decltype(CheckConst<C>(0)) ConstResult;                                       \
  33. public:                                                                                   \
  34.     enum { eIS_NOCONST = NoConstResult::value      };                                     \
  35.     enum { eIS_CONST   = ConstResult::value        };                                     \
  36.     enum { eIS_AVAILABLE = eIS_NOCONST | eIS_CONST };                                     \
  37. };
  38.  
  39. #define is_available(class_name, member_type, member_name)         has_##member_name<class_name, member_type>::eIS_AVAILABLE
  40. #define is_available_method(class_name, member_type, member_name)  has_##member_name<class_name, member_type>::eIS_NOCONST
  41. #define is_available_cmethod(class_name, member_type, member_name) has_##member_name<class_name, member_type>::eIS_CONST
  42.  
  43. //------------------------------------------------------------------------------------
  44.  
  45.  
  46. int g;
  47. struct A
  48. {
  49.     A():r(g){}
  50.  
  51.     void fooA(int);
  52.     void fooA(int)const;
  53.     void fooA();
  54.     void fooA()const;
  55.  
  56.     int v;
  57.     int& r;
  58.     int a[10];
  59.     int* p;
  60.     int** pp;
  61. private:
  62.     void private_foo();
  63. };
  64.  
  65. struct B : A
  66. {
  67.     int v;
  68.     int fooB(){ return 0; }
  69. };
  70.  
  71.  
  72. DETECTED_MEMBER(fooA);
  73. DETECTED_MEMBER(fooB);
  74. DETECTED_MEMBER(v);
  75. DETECTED_MEMBER(r);
  76. DETECTED_MEMBER(a);
  77. DETECTED_MEMBER(p);
  78. DETECTED_MEMBER(pp);
  79.  
  80. DETECTED_MEMBER(private_foo);
  81.  
  82.  
  83. int main()
  84. {
  85.     //синтаксис:  is_available(  имя_класса ,  тип_мембера  , имя_мембера)
  86.  
  87.     //вернет true если мембер доступен, иначе - false
  88.  
  89.     //---- детектирование данных
  90.     cout<< "is available int B.v ? "
  91.         << is_available(B,int,v)     <<endl;
  92.  
  93.     cout<< "is available int& B.r ? "
  94.         << is_available(B,int&,r)    <<endl;
  95.  
  96.     cout<< "is available int B.a[10] ? "
  97.         << is_available(B,int[10],a) <<endl;
  98.  
  99.     cout<< "is available int* B.p ? "
  100.         << is_available(B,int*,p)    <<endl;
  101.  
  102.     cout<< "is available int* B.pp ? "
  103.         << is_available(B,int**,pp)  <<endl;
  104.  
  105.     //---- детектирование методов
  106.     cout<< "is available void B.fooA(int) or void B::fooA(int)const ? "
  107.         <<is_available(B,void(int),fooA) <<endl;
  108.  
  109.     cout<< "is available void B.fooA(int) ? "
  110.         << is_available_method(B,void(int),fooA) <<endl;
  111.  
  112.     cout<< "is available void B.fooA(int)const ? "
  113.         << is_available_cmethod(B,void(int),fooA) <<endl;
  114.  
  115.     cout<< "is available int B.fooB() ? "
  116.         << is_available_method(B,int(),fooB) <<endl;
  117.  
  118.     cout<< "is available void B.private_foo() ? "      
  119.         << is_available(B,void(),private_foo) <<endl;
  120. }
  121.  
  122.  
  123.  
Success #stdin #stdout 0s 3340KB
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Standard input is empty
stdout
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is available int B.v ? 1
is available int& B.r ? 1
is available int B.a[10] ? 1
is available int* B.p ? 1
is available int* B.pp ? 1
is available void B.fooA(int) or void B::fooA(int)const ? 1
is available void B.fooA(int) ? 1
is available void B.fooA(int)const ? 1
is available int B.fooB() ? 1
is available void B.private_foo() ? 0
https://ideone.com/ObElnu
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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