C++ runtime type switching (avoiding switch)

Question

I\'ve been into C++ for some years but I have not found yet the solution to a problem I constantly have. Know how to solve it would be awesome.

What I have at the mo

Answer 1

To expand on my comment, ideally we'd have compile-time reflection and be able to write a generic dispatch function. In its absence, one option is to unfortunately use macros to do that for you using the X Macro pattern:

#define LIST_OF_CASES   \
    X_ENUM(kValue0)     \
    X_ENUM(kValue1)     \
    X_ENUM(kValue2)


enum MyEnum
{
#   define X_ENUM(a) a,
    LIST_OF_CASES
#   undef X_ENUM
};

void dispatch(MyEnum val)
{
    switch (val)
    {
#       define X_ENUM(a) case a: processData(); break;
        LIST_OF_CASES
#       undef X_ENUM
    default:
        // something's really wrong here - can't miss cases using this pattern
    }
}

One benefit of this approach is that it scales to large numbers of enumerations, it gets really hard to omit a case, and that you can attach extra information by using a multi-argument X_ENUM macro.

I know you said you'd like to avoid macros, but the alternative without virtual functions then is to have some sort of a static table of function pointers indexed by the enum, and that is just a virtual function in disguise (with admittedly lower overhead, but still suffering the cost of an indirect function call).