为什么我的代码在运行时保持循环

Question

#include <iostream>
#include <string>
#include <ctime>
using namespace std;
class PVR {
private:
int channel;
public:
PVR() {
cout << "Select the channel ==> ";
cin >> channel;
cout << endl;
}
};
class DVR  {
private:
string position;
public:
DVR() {
cout << "Select the position ==> ";
cin >> position;
cout << endl;
}
};
class Oven {
private:
string food;
public:
Oven() {
cout << "What do you want to bake? ==> ";
cin >> food;
cout << endl;
}
};

class PrgDevice {
private:
tm startTime;
tm stopTime;
int choice;
int choice1;
char c;
public:
void dateTime() {
cout << "Enter start date and start time: ";
cin >> startTime.tm_mday >> startTime.tm_mon >> startTime.tm_year >> startTime.tm_hour >> startTime.tm_min >> startTime.tm_sec;
cout << "Enter stop date and stop time: ";
cin >> stopTime.tm_mday >> stopTime.tm_mon >> stopTime.tm_year >> stopTime.tm_hour >> stopTime.tm_min >> stopTime.tm_sec;
}
void mainMenu() {
while (choice != 3) {
cout << "Main menu options: n";
cout << "      1. Select a device to program (contains a submenu)" << endl;
cout << "      2. Display current status of all devices" << endl;
cout << "      3. Exit" << endl;
cout << "Enter your option => ";
cin >> choice;
if (choice == 1) {
subMenu();
}
else if (choice == 2) {
cout << choice;
}
else {
}
}
}
void subMenu() {
do {
cout << "Select a device:" << endl;
cout << "         1. PVR" << endl;
cout << "         2. Camera DVR" << endl;
cout << "         3. Oven" << endl;
cout << "Enter your option => ";
cin >> choice1;
if (choice1 == 1) {
PVR n1;
}
else if (choice1 == 2) {
DVR n2;
}
else {
Oven n3;
}
dateTime();
cout << endl;
cout << "Another device to program Y/N ? => ";
cin >> c;
}
while(c == 'Y' || c == 'y');
}
};

int main() {
PrgDevice obj1;
obj1.mainMenu();
system("pause");
return 0;
}

这是我的输出

Main menu options: 
1. Select a device to program (contains a submenu)
2. Display current status of all devices
3. Exit
Enter your option => 1
Select a device:
1. PVR
2. Camera DVR
3. Oven
Enter your option => 1
Select the channel ==> 23
Enter start date and start time: 12:01:19 20:00:00

当我按回车键时，我的程序只是循环，我不知道为什么会这样

Answer 1

问题是您的程序希望用户输入时间和日期作为空格分隔的值，但您将它们输入为冒号分隔的值。

这意味着

cin >> startTime.tm_mday >> startTime.tm_mon >> ...

会将12读入startTime.tm_mday，但随后输入中有一个与startTime.tm_mon类型不匹配的:。这将停止所有输入读取，将:留在输入缓冲区中以供下一次输入操作使用。

下一个输入操作适用于stopTime由于输入缓冲区中的:而立即失败。因此，您又回到了subMenu函数中，冒号将被读入c。并且':'不等于'Y'或'y'，因此循环结束，subMenu函数返回到您再次打印菜单的mainMenu。

Answer 2

这对我来说不像是一个无限循环。尝试输入开始时间，如下所示：

12 1 19  20 0 0

CIN 不会神奇地处理输入中的"："字符，因此您可能需要读取整行，并解析出"："字符。