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  1. #include <iostream>
  2. #include <map>
  3. using namespace std;
  4.  
  5. template<typename T>
  6. struct ValueProxy
  7. {
  8. 	ValueProxy(T& v)
  9. 		: value(v)
  10. 	{
  11. 	}
  12.  
  13. 	operator T&()
  14. 	{
  15. 		return value;
  16. 	}
  17.  
  18. 	operator const T&() const
  19. 	{
  20. 		return value;
  21. 	}
  22.  
  23. 	ValueProxy& operator=(const T& nv)
  24. 	{
  25. 		value = nv;
  26. 		return *this;
  27. 	}
  28.  
  29. 	T& value;
  30. };
  31.  
  32. template<typename Key, typename Value>
  33. struct SomeMap
  34. {
  35. 	// Helpers
  36. 	using parent_t = std::map<Key, Value>;
  37. 	parent_t holder;
  38.  
  39. 	// Part of interest
  40. 	ValueProxy<Value> operator[](const Key& key)
  41. 	{
  42. 		return {holder[key]};
  43. 	}
  44. };
  45.  
  46. void modify(int& a) {// базовый метод
  47.     a += 5;
  48. }
  49.  
  50. void dump(const SomeMap<int,int> &mp)
  51. {
  52. 	for (auto v : mp.holder)
  53. 	{
  54. 		cout << std::get<1>(v) << ' ';
  55. 	}
  56. 	cout << endl;
  57. }
  58.  
  59. int main() 
  60. {
  61. 	SomeMap<int, int> mp;
  62.  
  63. 	// Proxy test 1
  64. 	mp[2] = 100;
  65. 	dump(mp);
  66.  
  67. 	// Proxy test 2
  68. 	modify(mp[2]);
  69. 	dump(mp);
  70.  
  71. 	// Proxt test 3
  72. 	mp[2] = mp[2] + 100;
  73. 	dump(mp);
  74.  
  75.  
  76.  
  77. 	return 0;
  78. }
  79.  
Success #stdin #stdout 0s 3416KB
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https://ideone.com/DBTILc
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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