Question

I have a constructor which looks like:

RandomClass(const int16_t var1, const SecondClass& var2);

I need to pass a default argument to the second parameter, so currently I do something like this:

RandomClass(const int16_t var1, const SecondClass& var2 = *(new SecondClass(*(new std::unordered_map<int16_t, double>())));

which is incredibly awkward. Note that I do not want to use an overloaded constructor, or change the second parameter from a reference to a pointer.

What would an elegant way of passing the default parameter be?

Answer 1

You are allowed to bind a const reference to a temporary:

RandomClass(const int16_t var1, const SecondClass& var2 = SecondClass(std::unordered_map<int16_t, double>()));

Of course this assumes that you either copy var2 into a member or do not use it after the constructor exits. If this is not the case, then something is wrong in your design. Perhaps using a raw pointer or a shared/weak_ptr is more appropriate.