C++11—Scoped enums

In Fig. 6.10, we introduced enums. One problem with enums (also called unscoped enums) is that multiple enums may contain the same identifiers. Using such enums in the same program can lead to naming collisions and logic errors. To eliminate these problems, C++11 introduces so-called scoped enums, which are declared with the keywords enum class (or the synonym enum struct). For example, we can define the Status enum of Fig. 6.10 as:

To reference a scoped enum constant, you must qualify the constant with the scoped enum’s type name (Status) and the scope-resolution operator (::), as in Status::CONTINUE. This explicitly identifies CONTINUE as a constant in the scope of enum class Status. Thus, if another scoped enum contains the same identifier for one of its constants, it’s always clear which version of the constant is being used.