Type of a global object dependent on boolean flag (determined at runtime)

Question

I want to do something like the following

if (flag) {
  type1_t object = .....
} else {
  type2_t object = .....
}

// do the same thing with object

type1_t and type2_t are custom classes. The problem with the above snippet is object remains local to each if else clause, but I can't define it above the if-else because the type is dependent on flag.

Late edit: It seems I can't use C++17 features in this codebase I'm working with so the std::variant idea won't work.

Answer 1

you can use std::variant here. Something like

std::variant<std::monostate, type1_t, type2_t> object;
if (flag) { ... } else { ... }

Notice the usage of std::monostate. That's because std::variant's default constructor uses the first alternative's default constructor. std::monostate is here to avoid that.

Besides, std::auto_ptr is deprecated long time ago. std::unique_ptr is much better