Correct usage(s) of const_cast<>

Question

As a common rule, it is very often considered a bad practice to use const_cast<>() in C++ code as it reveals (most of the time) a flaw in the design.

Answer 1

Like others have said, its primary purpose is to remove const from objects in order to pass to non-const correct functions you know won't modify the argument.

There is a trick (by Meyers?) to avoid code duplication, and it goes like this:

struct foo
{
    const return_type& get(void) const
    {
        // fancy pants code that you definitely
        // don't want to repeat

        return theValue; // and got it
    }

    return_type& get(void)
    {
        // well-defined: Add const to *this,
        // call the const version, then
        // const-cast to remove const (because
        // *this is non-const, this is ok)
        return const_cast(static_cast(*this).get());
    }
};