Access enum values in C++98 and C++11

Question

I have a set of enum values defined in the "Foo" class (below).

namespace Fii
{
    class Foo 
    {
        struct Bar
        {
            enum Baz
            {
                BAZ1,
                BAZ2, 
                BAZ3
            };
        };
    };
};

I am using a struct to reduce the scope of Baz enum values as well as show there are a group of related values.

My objective is to assign a value from an enum type to a variable. Using the class definition above, one can do this:

Fii::Foo::Bar::Baz myValue = Fii::Foo::Bar::BAZ1 (Works in both C++98 and C++11)

However, I feel that:

• At first glance, myValue seems to be initialized as a Fii::Foo::Bar but this is just because enum are a hack to group related constants in the parent (Bar in this case)

To improve readiness, I I re-factored the code to:

namespace Fii
{
    class Foo 
    {
        enum Baz
        {
            BAZ1,
            BAZ2, 
            BAZ3
        };
    };
};

Using this new class definition, one can do this:

Fii::Foo::Baz myValue = Fii::Foo::Baz::BAZ1 (Works in C++11 only)
Fii::Foo::Baz myValue = Fii::Foo::BAZ1 (Should work on C++98 and C++11 - not tested)

Q1) Why is Fii::Foo::Bar::Baz myValue = Fii::Foo::Baz::BAZ1 only working on C++11 ?

Q2) In C++98, is there a way to write Fii::Foo::Baz myValue = Fii::Foo::Baz::BAZ1 ? You are allowed to make any changes you like in the class definition.

Environment: - Clang compiler with C++11 support - Xcode 4 - Mac OS OS 10.8

Answer 1

C++11 adds class enums. It also adds a new way of accessing old-style enum values, which is what you are seeing here.

enum Foo { FOO1, FOO2, FOO3 }; // old-style enum

Foo f1 = Foo::FOO1; // OK in C++11, error in C++98.
Foo f2 = FOO1; // OK in C++98 and C++11 (for backward compatibility)