C++ 형변환 오버로딩 (Typecasts Overloading)

형변환 오버로딩 (Typecasts Overloading)

• (int)객체, int(객체), static_cast<int>(객체) 등의 형태로 형변환을 할 수 있게 해준다.

• 묵시적 형변환도 가능해진다.

---

예제

  #include <iostream>

  class Cents
  {
    int cents_;

  public:
    Cents(int cents = 0) { cents_ = cents; }

    operator int()
    {
      std::cout << "cast here" << std::endl;
      return cents_;
    }
  };

  void    printInt(const int& value)
  {
    std::cout << value << std::endl;
  }

  int        main()
  {
    using namespace std;

    Cents    cents(7);

    printInt(cents);

    int value;

    value = (int)cents;
    value = int(cents);
    value = static_cast<int>(cents);
  }

  /* stdout
  cast here
  7
  cast here
  cast here
  cast here
  */

• 다른 객체로의 형변환 오버로딩도 가능하다.

  #include <iostream>
  
  class Cents
  {
    int cents_ = 0;
  
  public:
    Cents(const int& cents = 0) { cents_ = cents; }
  
    operator int()
    {
      std::cout << "cast here" << std::endl;
      return cents_;
    }
  };
  
  class Dollars
  {
    int    dollars_ = 0;
  
  public:
    Dollars(const int& dollars = 0) { dollars_ = dollars; }
  
    operator Cents()
    {
      return Cents(dollars_ * 100);
    }
  };
  
  void    printInt(const int& value)
  {
    std::cout << value << std::endl;
  }
  
  int        main()
  {
    using namespace std;
  
    Dollars    dol(2);
    Cents    cents(dol);
  
    printInt(cents);
  }
  
  /* stdout
  cast here
  200
  */