How cast C++ class to intrinsic type

问题

Basic C++ class question:

I have simple code currently that looks like something like this:

typedef int sType;
int array[100];

int test(sType s)
{
  return array[ (int)s ];
}

What I want, is to convert "sType" to a class, such that the "return array[ (int)s ]" line does not need to be changed. e.g. (pseudocode)

class sType
{
  public:
    int castInt()
    {
      return val;
    }
    int val;
}


int array[100];    
int test(sType s)
{
  return array[ (int)s ];
}    

Thanks for any help.

回答1:

class sType
{
public:
    operator int() const { return val; }

private:
    int val;
};

回答2:

class sType
{
  public:
    operator int() const
    {
      return val;
    }
    int val;
};

To make s = 5 work, provide a constructor that takes an int:

class sType
{
  public:

    sType (int n ) : val( n ) {
    }

    operator int() const
    {
      return val;
    }
    int val;
};

The compiler will then use that constructor whenever it need to convert an sType to an int.

来源：https://stackoverflow.com/questions/4469894/how-cast-c-class-to-intrinsic-type