c++ - 访问结构中定义的枚举值

Question

如果我有以下内容:

struct LineChartScene::LineChartSceneImpl
{
    enum ContextMenuAction {ShowLabels, ShowPoints, SaveAsImage};
};

如何在 LineChartScene::LineChartSceneImpl 结构之外访问 ShowLabels、ShowPoints 等？我认为 LineChartScene::LineChartSceneImpl::ContextMenuAction::ShowLabels 会起作用，但它不起作用。我正在使用 C++，Qt Creator 2.2.1。

Answer 1

struct LineChartScene::LineChartSceneImpl
{
    enum ContextMenuAction {ShowLabels, ShowPoints, SaveAsImage};
};

用作

LineChartScene::LineChartSceneImpl::ShowLabels

关于您的信息，C++11 also has strong typed enums精确地具有您期望的命名空间语义:

enum class Enum2 : unsigned int {Val1, Val2};

The scoping of the enumeration is also defined as the enumeration name's scope. Using the enumerator names requires explicitly scoping. Val1 is undefined, but Enum2::Val1 is defined.

Additionally, C++11 will allow old-style enumerations to provide explicit scoping as well as the definition of the underlying type:

enum Enum3 : unsigned long {Val1 = 1, Val2};

The enumerator names are defined in the enumeration's scope (Enum3::Val1), but for backwards compatibility, enumerator names are also placed in the enclosing scope.