Question

For example:

void Date::month(unsigned int inMonth) {
    assert(inMonth <= 12);
    _month = inMonth;
}

If this is not good practice, what is the correct way to go about this?

Answer 1

You shouldn’t use assert to ensure that an argument to a public member function is valid. The reason is that there’s no way for clients of your class to react to a failed assertion in any meaningful way (the fact that asserts are removed from release builds does not help either).

As a rule of thumb, assert should only be used for things that are strictly under your control (e.g., an argument of a private method).

In this case you’re better off throwing a std::invalid_argument exception:

void Date::month(unsigned int month) 
{
    if(month == 0 || month > 12)
    {
        throw std::invalid_argument("a month must be in the [1-12] range"); 
    }
    _month = month;
}