C++:在类内、类外应用枚举

Question

class Stepper {
    public:
    enum microstepping {
        FULL,
        HALF,
        QUARTER
    };
    int stepsPerStep;

    Stepper(microstepping _microstepping) {
        switch(_microstepping){
        case FULL:
            stepsPerStep = 1;
            break;
        case HALF:
            stepsPerStep = 2;
            break;
        case QUARTER:
            stepsPerStep = 4;
            break;
        }
    }

};

void main() {
    Stepper stepperA(FULL);//Problem shows here

}

/* 我正在尝试使用枚举在类的特定实例中设置内部变量。问题是当我尝试使用它时，枚举在类外无法识别。在类外声明枚举不是一种选择。 */

Answer 1

您需要使用 Stepper 范围对其进行限定 -

class Stepper {
    public:
    enum microstepping {
        FULL,
        HALF,
        QUARTER
    };
    int stepsPerStep;

    Stepper(microstepping _microstepping) {
        switch(_microstepping){
        case FULL:
            stepsPerStep = 1;
            break;
        case HALF:
            stepsPerStep = 2;
            break;
        case QUARTER:
            stepsPerStep = 4;
            break;
        }
    }

};

int main() {
    Stepper stepperA(Stepper::FULL);
}

并尽可能使用enum class -

class Stepper {
    public:
    enum class microstepping {
        FULL,
        HALF,
        QUARTER
    };
    int stepsPerStep;

    Stepper(microstepping _microstepping) {
        switch(_microstepping){
        case microstepping::FULL:
            stepsPerStep = 1;
            break;
        case microstepping::HALF:
            stepsPerStep = 2;
            break;
        case microstepping::QUARTER:
            stepsPerStep = 4;
            break;
        }
    }

};

int main() {
    Stepper stepperA(Stepper::microstepping::FULL);
}