c++ - 使用 getline 的问题

Question

我正在为我的 C++ 类(class)介绍做期末项目，但我的代码有问题。 getline 似乎没有用，尽管我输入它的方式和我在其他地方看到的一样。这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);

当它运行时，cout 行显示在屏幕上(它只是闪烁，但在您看到它停留后带有一个 system("PAUSE"))，然后它退出 if 循环并返回到主循环。我不知道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。我知道这很艰难；我刚开始。

// 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;
}

Answer 1

由于您执行了 cin >> menuInput，这只是读取您的 menuInput 编号，但将新行 \n 保留在缓冲区中。当您调用 getline 时，它会返回空行，因为 \n 仍在等待。当您混合使用 getline 时，您应该在使用 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);

您需要将其添加到每个从 std::cin 读取的 getline 调用中。这应该可以解决您的问题。

除此之外，还有一些建议:

• 不要使用 system("cls") 或 system("pause")，尝试将其删除，但您的控制台将无法清除。
• 将您的代码重构为单独的函数，不要将所有内容都塞入 main() 中。例如，在基于 menuInput 的 cin >> menuInput 之后，您可以调用其中一个函数:manageGroceries(...), manageHardware(...), manageChores(...)。