c++ - 在 C++ 中使用类和枚举

Question

努力寻找在 C++ 中实现类和枚举的正确方法。

class CrossingGateRoad {
    public:
        boolean PowerOn(byte relayNumber) {
            digitalWrite(relayNumber, RELAY_ON);
            return true;
        }
        boolean PowerOff(byte relayNumber) {
            digitalWrite(relayNumber, RELAY_OFF);
            return true;
        }
};

然后我尝试创建一个枚举，如下所示:

enum {
    CROSSINGZONE_CLEAR, // no train in crossing area, also initialized state
    CROSSINGZONE_OCCUPIED, // train detected by the entry sensor
    CROSSINGZONE_EXITING  // train detected by the exit sensor, when sensor clears, state = CLEAR
};

在 C# 中，我会命名我的枚举并指定值:

public enum CommodityIndexSector
{
    Currency = 1,
    StockIndex = 2,
    GovernmentBond = 3,
    Metals = 4,
    Energy = 5,
    Grains = 6,
    Softs = 7,
    Meats = 8,
    Other = 9
}

我会像这样访问它.... enumname.enumvalue。我也不是 100% 确定类(class)看起来正确。

Answer 1

在 C++ 中，enum 值出现在它们的外部范围内。如果你有

enum {
    CROSSINGZONE_CLEAR, // no train in crossing area, also initialized state
    CROSSINGZONE_OCCUPIED, // train detected by the entry sensor
    CROSSINGZONE_EXITING  // train detected by the exit sensor, when sensor clears, state = CLEAR
};

几乎等同于具有 #define 值。

要在其他地方指定枚举类型，您需要为其命名:

enum CrossingZones {
  // ^^^^^^^^^^^^^
    CROSSINGZONE_CLEAR, // no train in crossing area, also initialized state
    CROSSINGZONE_OCCUPIED, // train detected by the entry sensor
    CROSSINGZONE_EXITING  // train detected by the exit sensor, when sensor clears, state = CLEAR
};

你可以引用具体的枚举类型:

CrossingZones crossingZones = CROSSINGZONE_CLEAR;

---

关于值的更直观的声明，是按照当前标准使用枚举类:

enum class CrossingZones {
  // ^^^^^
    CROSSINGZONE_CLEAR, // no train in crossing area, also initialized state
    CROSSINGZONE_OCCUPIED, // train detected by the entry sensor
    CROSSINGZONE_EXITING  // train detected by the exit sensor, when sensor clears, state = CLEAR
};

并在范围内使用它们:

CrossingZones crossingZones = CrossingZones::CROSSINGZONE_CLEAR;
                           // ^^^^^^^^^^^^^^^