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  1.  
  2. #include <iostream>
  3.  
  4. template <class MemPtr, MemPtr p>
  5. struct Accessor {
  6.     static MemPtr value() {
  7.         return p;
  8.     }
  9. };
  10.  
  11. // ------------------------------------------------------
  12. // Target Class
  13. // privateメンバにアクセスされるクラス
  14. struct A {
  15.     A(int mem1, int mem2):mem1(mem1), mem2(mem2) {}
  16.     void print() const { 
  17.         std::cout << "mem1 = " << mem1 << " mem2 = " << mem2 << std::endl;
  18.     }
  19.     int mem1;
  20.     int mem2;
  21. };
  22.  
  23. int main() {
  24.     A a(1, 2);
  25.     // メンバポインタを経由してのアクセス
  26.     std::cout << a.*&A::mem2 << std::endl;
  27.     // Accessorを経由して (設定済みの )mem にアクセス
  28.     std::cout << a.*Accessor<int A::*, &A::mem1>::value() << std::endl;
  29.     std::cout << a.*Accessor<int A::*, &A::mem2>::value() << std::endl;
  30.     a.*Accessor<int A::*, &A::mem1>::value() = 3;
  31.     a.*Accessor<int A::*, &A::mem2>::value() = 4;
  32.     a.print();
  33. }
  34. // Output:
  35. /*
  36. 2
  37. 1
  38. 2
  39. mem1 = 3 mem2 = 4
  40. */
  41.  
Success #stdin #stdout 0.02s 2724KB
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Standard input is empty
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2
1
2
mem1 = 3 mem2 = 4
https://ideone.com/dGRqg
language:
C++ (gcc 8.3)
created:
14 years ago
visibility:
public

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