我正在研究我的c ++类简介的最终项目，我的代码存在问题。 getline似乎没有起作用，虽然我输入的方式和其他很多次一样，并且已经在其他地方看过了。以下是有问题的代码部分
if (groceryMenu == 2)
{
string groceryItem;
system("CLS");
cout << "Enter what you would like to add to the grocery list: " << endl;
getline(cin, groceryItem);
groceryVector.push_back(groceryItem);
当这个运行时，cout线显示在屏幕上（它只是闪烁，但在你看到它停留后有一个系统（“PAUSE”）），但随后它退出if循环并返回到主循环。我无法弄清楚我在这里做错了什么。任何帮助表示赞赏：）
这是我的其余代码，如果有帮助的话。我知道它很粗糙;我刚刚开始。
// 7.3 lists and vectors
#include<iostream>
#include<iomanip>
#include<string>
#include<vector>
#include<fstream>
#include "stdafx.h"
using namespace std;
int main()
{
int menuInput = 0;
int exitProgram = 0;
vector<string> groceryVector;
vector<string> hardwareVector;
vector<string> choreVector;
fstream inputFile, outputFile;
string groceryInput;
inputFile.open("grocery.txt");
while (getline(inputFile, groceryInput))
{
groceryVector.push_back(groceryInput);
}
inputFile.close();
string hardwareInput;
inputFile.open("hardware.txt");
while (getline(inputFile, hardwareInput))
{
hardwareVector.push_back(hardwareInput);
}
inputFile.close();
string choreInput;
inputFile.open("chore.txt");
while (getline(inputFile, choreInput))
{
choreVector.push_back(choreInput);
}
inputFile.close();
while (exitProgram == 0)
{
system("CLS");
cout << "List Manager" << endl;
cout << "Press 1 to manage the grocery list." << endl;
cout << "Press 2 to manage the hardware store list." << endl;
cout << "Press 3 to manage the chore list." << endl;
cout << "Press 4 to exit." << endl;
cin >> menuInput;
if (menuInput == 4)
{
system("CLS");
cout << "Now exiting program." << endl;
exitProgram = 2;
break;
}
while (menuInput == 1)
{
system("CLS");
int groceryMenu = 0;
cout << "Press 1 to read the grocery list." << endl;
cout << "Press 2 to add an item to the list." << endl;
cout << "Press 3 to delete an item from the list." << endl;
cout << "Press 4 to return to the main menu." << endl;
cin >> groceryMenu;
if (groceryMenu == 1)
{
system("CLS");
for (string groceryList : groceryVector)
{
cout << groceryList << endl;
}
system("PAUSE");
}
if (groceryMenu == 2)
{
string groceryItem;
system("CLS");
cout << "Enter what you would like to add to the grocery list: " << endl;
getline(cin, groceryItem);
groceryVector.push_back(groceryItem);
}
if (groceryMenu == 3)
{
int eraseLine = 0;
system("CLS");
cout << "What line would you like to erase from the list?" << endl;
cin >> eraseLine;
groceryVector.erase(groceryVector.begin() + (eraseLine - 1));
}
outputFile.open("grocery.txt");
for (string groceryList : groceryVector)
{
outputFile << groceryList << endl;
}
outputFile.close();
if (groceryMenu == 4)
{
menuInput = 0;
}
}
while (menuInput == 2)
{
system("CLS");
int hardwareMenu = 0;
cout << "Press 1 to read the hardware list." << endl;
cout << "Press 2 to add an item to the list." << endl;
cout << "Press 3 to delete an item from the list." << endl;
cout << "Press 4 to return to the main menu." << endl;
cin >> hardwareMenu;
if (hardwareMenu == 1)
{
system("CLS");
for (string hardwareList : hardwareVector)
{
cout << hardwareList << endl;
}
system("PAUSE");
}
if (hardwareMenu == 2)
{
string hardwareItem;
system("CLS");
cout << "Enter what you would like to add to the hardware list: " << endl;
getline(cin, hardwareItem);
hardwareVector.push_back(hardwareItem);
}
if (hardwareMenu == 3)
{
int eraseLine = 0;
system("CLS");
cout << "What line would you like to erase from the list?" << endl;
cin >> eraseLine;
hardwareVector.erase(hardwareVector.begin() + (eraseLine - 1));
}
outputFile.open("hardware.txt");
for (string hardwareList : hardwareVector)
{
outputFile << hardwareList << endl;
}
outputFile.close();
if (hardwareMenu == 4)
{
menuInput = 0;
}
}
while (menuInput == 3)
{
system("CLS");
int choreMenu = 0;
cout << "Press 1 to read the chore list." << endl;
cout << "Press 2 to add an item to the list." << endl;
cout << "Press 3 to delete an item from the list." << endl;
cout << "Press 4 to return to the main menu." << endl;
cin >> choreMenu;
if (choreMenu == 1)
{
system("CLS");
for (string choreList : choreVector)
{
cout << choreList << endl;
}
system("PAUSE");
}
if (choreMenu == 2)
{
string choreItem;
system("CLS");
cout << "Enter what you would like to add to the chore list: " << endl;
getline(cin, choreItem);
choreVector.push_back(choreItem);
}
if (choreMenu == 3)
{
int eraseLine = 0;
system("CLS");
cout << "What line would you like to erase from the list?" << endl;
cin >> eraseLine;
choreVector.erase(choreVector.begin() + (eraseLine - 1));
}
outputFile.open("chore.txt");
for (string choreList : choreVector)
{
outputFile << choreList << endl;
}
outputFile.close();
if (choreMenu == 4)
{
menuInput = 0;
}
}
}
return 0;
}
答案 0 :(得分：2)
由于您执行cin >> menuInput，因此只需读入menuInput编号，但仍将新行\n保留在缓冲区中。当您致电getline时，它会返回空行，因为还有\n在等待。混合getline时，应在使用getline之前清除输入缓冲区：
cout << "Enter what you would like to add to the grocery list: " << endl;
cin.ignore(); // <<== you need this!
getline(cin, groceryItem);
您需要将其添加到从getline读取的每个std::cin来电。
这应该可以解决你的问题。
除此之外，还有一些建议：
system("cls")或system("pause")，尝试将其删除，但您的控制台无法清除。main()中。例如，在基于cin >> menuInput的{{1}}之后，您可以调用其中一项功能：menuInput，manageGroceries(...)，manageHardware(...)。答案 1 :(得分：0)
main函数中。将其拆分为较小的函数，这样可以重用大量代码，最终代码将缩小3倍。注意＆＃34;杂货＆＃34;，＆＃34;硬件＆＃34;和＆＃34;家务＆＃34;正在做同样的事情。唯一的区别是装饰性的，可以参数化。system("cls")它是寡妇特有的，并没有做你期望的事情（它只会产生这种感觉）。这是因为不了解标准输入/输出和控制台之间的区别。我猜测你输入了无效值，将标准输入的状态改变为无法读取数据的状态。
使用cin.clear()清除输入上的错误状态，cin.synch()清除（忽略）在控制台缓冲区中等待的所有数据，因此cin上的下一次读取操作将读取新提供的数据控制台。