What is a handle in C++?

Question

I have been told that a handle is sort of a pointer, but not, and that it allows you to keep a reference to an object, rather than the object itself. What is a more elaborat

Answer 1

A handle is a pointer or index with no visible type attached to it. Usually you see something like:

 typedef void* HANDLE;
 HANDLE myHandleToSomething = CreateSomething();

So in your code you just pass HANDLE around as an opaque value.

In the code that uses the object, it casts the pointer to a real structure type and uses it:

 int doSomething(HANDLE s, int a, int b) {
     Something* something = reinterpret_cast(s);
     return something->doit(a, b);
 }

Or it uses it as an index to an array/vector:

 int doSomething(HANDLE s, int a, int b) {
     int index = (int)s;
     try {
         Something& something = vecSomething[index];
         return something.doit(a, b);
     } catch (boundscheck& e) {
         throw SomethingException(INVALID_HANDLE);
     }
 }