C++ enum class: Purpose and Advantages

In C++, the enum class is a new feature for enum types that introduces scope and prevents naming conflicts, providing stronger type safety.

In traditional C++ enum types, enum values are globally visible and not restricted by namespaces. This can lead to naming conflicts for enum values, especially when the same values are used in different libraries or namespaces. Additionally, enum types can be implicitly converted to integer types, which may result in incorrect usage.

The enum class solves these issues by introducing scope qualification, ensuring that the names of enum values are located within the scope of the enum type. This means that different enum types can have the same names without conflicts. Furthermore, enum class does not allow implicit conversion to integer types, and can only be used through explicit type casting.

Here is an example code using enum class:

enum class Color { Red, Green, Blue };

Color c = Color::Red;
// 不会发生隐式转换为整数类型
int i = static_cast<int>(c); // 正确
int j = c; // 错误

switch (c) {
    case Color::Red:
        // 处理红色
        break;
    case Color::Green:
        // 处理绿色
        break;
    case Color::Blue:
        // 处理蓝色
        break;
}

In summary, the purpose of enum class is to introduce scope limitations for enumeration types, avoid naming conflicts, and provide stronger type safety.