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dinotom
dinotom

Reputation: 5162

Using classes and enums in C++

Struggling a bit with the proper way to implement a class and an enum in C++.

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

and then I'm trying to create an enum as follows:

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
};

In C# I would name my enum and specify the values:

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

and I would access it like so.... enumname.enumvalue. I'm not 100% sure the class looks right either.

Upvotes: 0

Views: 104

Answers (3)

Francesco Argese
Francesco Argese

Reputation: 656

You can use the following code to declare the enum:

typedef 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
} EnumName;

abd then access to its values through the following code:

EnumName::CROSSINGZONE_OCCUPIED

Upvotes: -1

πάντα ῥεῖ
πάντα ῥεῖ

Reputation: 1

In c++ enum values appear at their outer scope. If you have 

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
};

pretty much equivalent to have #define values.

To specify an enum type somewhere else you need to name it:

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
};

and you can reference the specific enum type:

CrossingZones crossingZones = CROSSINGZONE_CLEAR;

A more intuitive declaration regarding the values, is to have enum class as for the current standard:

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
};

and use these from scope:

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

Upvotes: 2

wally
wally

Reputation: 11002

In c++11 you can now use enum class and you may also specify the values for it. However you will need a cast to get the value back.

enum class Crossing_zone {
    clear = 0,
    occupied = 2,
    exiting = 1
};

int main()
{
    auto myenumvar = Crossing_zone::occupied;
    return 0;
}

Upvotes: 0

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