如何在 C++ 中将状态输入到枚举类型的变量中？

Question

#include <iostream>
enum Day { Mon = 1, Tue, Wed, Thu, Fri, Sat, Sun };
void printa(Day day);
int main() {
    enum Day day = Sun;
    printa(day);

    return 0;
}
void printa(Day day) {
    if (day > Fri)
        std::cout << "weekend" << std::endl;
    else
        std::cout << "weekdays" << std::endl;
}

See above code.

Day is defined as a variable of type enum.

The value of “Sun” is allocated to day, which is 7.

So as a result, "weekend" is printed.

Now I want this: I input a value (from 1 to 7) to day, that is, give it a state.

Here is the code:

#include <iostream>
enum Day { Mon = 1, Tue, Wed, Thu, Fri, Sat, Sun };
void printa(Day day);
int main() {
    enum Day day = Sun;
    std::cin >> day; // Here is the added line
    printa(day);

    return 0;
}
void printa(Day day) {
    if (day > Fri)
        std::cout << "weekend" << std::endl;
    else
        std::cout << "weekdays" << std::endl;
}

It can't work.

Can anybody tell me why?

How can I input a state to a variable of enum type in C++ ?

Answer 1

You can't use cin direct to enum type, but you can do it to an int and static cast it to your enum type like shown below:

#include <iostream>

enum Day : uint16_t { Mon = 1, Tue, Wed, Thu, Fri, Sat, Sun };

void printa(Day day) {
     if (day > Fri)
        std::cout << "weekend" << std::endl;
     else
        std::cout << "weekdays" << std::endl;
}

int main() {
    uint16_t day = Sun;

    std::cin >> day;

    printa(static_cast<Day>(day));

    return 0;
}