C++: how to choose the constructor depending on the condition?

Question

Assume I have a class with different constructors:

class A
{
public:
    A(char* string)
    {
        //...
    }

    A(int value)
    {
        //..
    }

           


        

Answer 1

If the type has a default constructor, you can default-construct an object, immediately destruct it, and then construct it again with the appropriate constructor via placement-new:

A a;
a.~A();
if (isTrue())
{
    new(&a) A("string");
}
else
{
    new(&a) A(10);
}

The C++ standard has several examples similar to the above, just search for .~ and ->~.

Note that this is ultra evil. If your code ever gets reviewed, you are probably going to get fired.