Question

Suppose I have a data type enum TreeTypes { TallTree, ShortTree, MediumTree }.

And I have to initialize some data based on one particular tree type.

Currently I have written this code:

int initialize(enum TreeTypes tree_type) {
    if (tree_type == TallTree) {
        init_tall_tree();
    }
    else if (tree_type == ShortTree) {
        init_short_tree();
    }
    else if (tree_type == MediumTree) {
        init_medium_tree();
    }
    return OK;
}

But this is some kind of stupid code repetition. I am not using any of the powerful C++ capabilities like templates.

How could I write this code better?

Thanks, Boda Cydo.

Answer 1

Your code is OK for two or three values, but you are right, you need something more industrial strength when you have hundreds of them. Two possible solutions:

• use a class hierarchy, not enums – you can then use virtual functions and have the compiler work out which actual function to call

• create a map of enum -> function, which you initialise at startup – your function calls then become something like map[enum]->func()

Templates don’t work so well here, because you are trying to make a decision at run-time, whereas templates do their stuff at compile-time.