Question

版本-1：

// In this, the enum is declared globally

#include <iostream>
#include <string>

using namespace std;

enum Hand {RIGHT,LEFT};

class Batsman {
    public:
        Batsman(string s, Hand h) {
            name = s;
            hand = h; 
        }
        void setName(string s) {
            name = s;
        }
        void setHand(Hand h) {
            hand = h;
        }
        string getName() {
            return name;
        }
        Hand getHand() {
            return hand;
        }           
    private:
        string name;
        Hand hand;  
};

void main() {
    Batsman B1("Ryder",LEFT);
    Batsman B2("McCullum",RIGHT);
}

版本-2：

// In this, the enum is declared inside the class

#include <iostream>
#include <string>

using namespace std;

class Batsman {
    public:     
        enum Hand {RIGHT,LEFT};
        Batsman(string s, Hand h) {
            name = s;
            hand = h; 
        }
        void setName(string s) {
            name = s;
        }
        void setHand(Hand h) {
            hand = h;
        }
        string getName() {
            return name;
        }
        Hand getHand() {
            return hand;
        }           
    private:
        string name;
        Hand hand;  
};

void main() {
    Batsman B1("Ryder",LEFT);
    Batsman B2("McCullum",RIGHT);
}

错误：

D:\\Work Space\\C++\\C.cpp: In function `int main(...)':
D:\\Work Space\\C++\\C.cpp:33: `LEFT' undeclared (first use this function)
D:\\Work Space\\C++\\C.cpp:33: (Each undeclared identifier is reported only once
D:\\Work Space\\C++\\C.cpp:33: for each function it appears in.)
D:\\Work Space\\C++\\C.cpp:34: `RIGHT' undeclared (first use this function)

请告诉我两个实例中的更正，以便我能一劳永逸地理解这个概念。真的很感激。

Answer 1

对于第一种情况，代码compiles just fine for me（在修复main()的返回类型之后）。我不知道你在困扰哪些错误。

对于你的第二种情况，枚举是在类的范围内声明的

class Batsman {
public:     
    enum Hand {RIGHT,LEFT};
    // ...
};

因此您必须在main()中提供范围限定符：

int main() {
    Batsman B1("Ryder",Batsman::LEFT);
                    // ^^^^^^^^^
    Batsman B2("McCullum",Batsman::RIGHT);
                       // ^^^^^^^^^
}

_{另请注意，您应始终int作为main()的返回类型。}

使用枚举变量作为类数据成员会产生错误

1 个答案: