CODEWITHSUNDEEP
c++switch-statementconstants
Godfather
Godfather

Reputation: 1129

Using static const class instance for a switch / case

I have a class which acts a little like an enum, each instance of it has a unique int value which starts at 0 and increments at every new instance.

class MyEnumLikeClass
{
    static int NextId = 0;

    static const MyEnumLikeClass FIRST;
    static const MyEnumLikeClass SECOND;

    const int val_;

public :
    MyEnumLikeClass() : val_(NextId++)
    {
    }

    operator int() const
    {
        return val_;
    }

    //other methods (usually getters) omitted for clarity
}

I am trying to use it in a switch case so that I can do something like 

MyEnumLikeClass value;
switch(value)
{
    case MyEnumLikeClass::FIRST :
        break;
    case MyEnumLikeClass::SECOND :
        break;
    default :
}

I am getting "case value is not a constant expression" errors which seem to be because the compiler doesn't know the values at compile time.

Is there any way to get this to work?

Upvotes: 0

Views: 1281

Answers (1)

b4hand
b4hand

Reputation: 9770

The argument to a case statement must be an integral constant expression prior to C++11. The easiest way to do that is to use a const int or an actual enum. If you're using C++11 then you can simply use the built-in enum class support. See the scoped enumerations.

Upvotes: 2

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