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  1. #include <iostream>
  2. #include <iterator>
  3.  
  4. struct Foo;
  5.  
  6. template<typename Type>
  7. struct MemberPtrBase {
  8.     virtual ~MemberPtrBase() { }
  9.  
  10. 	virtual Type get() const = 0;
  11. 	virtual MemberPtrBase & set(Type const &) = 0;
  12. };
  13.  
  14. template<typename Class, typename RealType, typename CommonType>
  15. struct MemberPtr : MemberPtrBase<CommonType> {
  16. public:
  17. 	MemberPtr(Class * object, RealType(Class::*member))
  18. 	: m_object(object), m_ptr(member)
  19. 	{ }
  20.  
  21. 	CommonType get() const {
  22. 		return m_object->*m_ptr;
  23. 	}
  24.  
  25. 	MemberPtr & set(CommonType const & val) {
  26. 		m_object->*m_ptr = val;
  27. 		return *this;
  28. 	}
  29.  
  30. 	MemberPtr & operator=(RealType const & val) {
  31. 		return set(val);
  32. 	}
  33.  
  34. 	operator CommonType() const {
  35. 		return get();
  36. 	}
  37. private:
  38. 	Class * m_object;
  39. 	RealType (Class::*m_ptr);
  40. };
  41.  
  42. template<typename Class, typename... Types>
  43. struct MemberIterator {
  44. public:
  45. 	using CommonType = typename std::common_type<Types...>::type;
  46. public:
  47. 	MemberIterator(Class & obj, std::size_t idx, Types(Class::*...member))
  48. 	: m_object(obj), m_index(idx), m_members { new MemberPtr<Class, Types, CommonType>(&obj, member)... }
  49. 	{ }
  50.  
  51. 	MemberPtrBase<CommonType> & operator*() const {
  52. 		return *m_members[m_index];
  53. 	}
  54.  
  55. 	bool operator==(MemberIterator const & it) const {
  56. 		return (&m_object == &it.m_object) && (m_index == it.m_index);
  57. 	}
  58.  
  59. 	bool operator!=(MemberIterator const & it) const {
  60. 		return (&m_object != &it.m_object) || (m_index != it.m_index);
  61. 	}
  62.  
  63. 	MemberIterator & operator++() {
  64. 		++m_index;
  65. 		return *this;
  66. 	}
  67. private:
  68. 	Class & m_object;
  69. 	std::size_t m_index;
  70. 	MemberPtrBase<CommonType> * m_members[sizeof...(Types)];
  71. };
  72.  
  73. struct Foo {
  74. public:
  75. 	using iterator = MemberIterator<Foo, int, int, int, int>;
  76. public:
  77. 	Foo(int a, int b, int c, int d)
  78. 	: m_a(a), m_b(b), m_c(c), m_d(d)
  79. 	{ }
  80.  
  81. 	iterator begin() {
  82. 		return iterator(*this, 0, &Foo::m_b, &Foo::m_d, &Foo::m_c, &Foo::m_a);
  83. 	}
  84.  
  85. 	iterator end() {
  86. 		return iterator(*this, 4, &Foo::m_b, &Foo::m_d, &Foo::m_c, &Foo::m_a);
  87. 	}
  88. private:
  89. 	int m_a, m_b, m_c, m_d;
  90. };
  91.  
  92. int main(int argc, char ** argv) {
  93. 	Foo foo { 1, 2, 3, 4 };
  94.  
  95. 	for(auto & mem : foo) {
  96. 		std::cout << mem.get() << std::endl;
  97. 		mem.set(3);
  98. 	}
  99.  
  100. 	for(auto & mem : foo) {
  101. 		std::cout << mem.get() << std::endl;
  102. 	}
  103. }
Success #stdin #stdout 0s 3472KB
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https://ideone.com/LIye7v
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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