Question

我是C ++的初学者，我已经阅读了各种问题和解决方案，但我仍然无法让我的代码工作！问题是，如果我不包括已注释掉的cin.clear（）或cin.synch（），我的代码不会在开始的getline中停止。当我添加它们时，它会无限循环。有什么东西我不包括在内吗？这是我的源代码：

  #include <iostream>  
  #include <fstream>
  #include <string>
  #include <cctype>
  using namespace std;
  int main() {
string inputFileName, outputFileName, inData, outData, inWord, outWord;
ifstream inFile, testStream;
ofstream outFile;
bool outPutOpened = false;
char outChar; 
int shiftNum = 0, idx = 0;
do  {

    inWord.clear();
    outWord.clear();
    //cin.clear();
    //cin.sync();


    cout << "Available options: " << endl;
    cout << "1. ENCRYPT - Encrypt a file using Caesar Cypher" << endl // menu
    << "2. Quit - Exit the program" << endl << endl;
    cout << "   Enter keyword or option index: ";
    getline(cin, inWord); // get option
    outWord.resize(inWord.length());
    transform(inWord.begin(), inWord.end(), outWord.begin(), ::toupper); //capitalize
    if (outWord.compare("ENCRYPT") == 0 || outWord.compare("1") == 0) {
        cout << "CAESAR CYPHER PROGRAM" << endl
        << "======================" << endl << endl;
        do {                
            cout << "Provide the input file name: ";

            getline(cin, inputFileName);

            inFile.open(inputFileName.c_str());
            if (inFile.fail()) {
            cout << "Cannot open file, please try again!" << endl;
                inFile.clear();
            }
     }

            while (!inFile.is_open());

        getline(inFile, inData);

        do {
            cout << "Provide the output file name: ";
            cin >> outputFileName;

            testStream.clear();
            testStream.open(outputFileName.c_str());
            if(testStream.good()) {
            cout << "That file already exists, choose another" << endl;
                testStream.clear();
                testStream.close();
            }
            else {
                testStream.clear();
                testStream.close();
                outFile.open(outputFileName.c_str());
                if (outFile.good()) {
                    outPutOpened = true;
                }   
            }
        }
        while (!outPutOpened); 
        cout << "Enter the shift number: ";
        cin >> shiftNum;

        for (idx = 0; idx <= inData.length() - 1; idx++) {

            if  (inData[idx] >= 'a' && inData[idx] <= 'z') {
        outChar = (((inData[idx] - 'a') + shiftNum) % 26) + 'a';
                outFile.put(outChar);

            }
            else if (inData[idx] >= 'A' && inData[idx] <= 'Z'){
                outChar = (((inData[idx] - 'A') + shiftNum) % 26) + 'A'; 
                outFile.put(outChar);
            }
            else {
                outFile.put(inData[idx]);
            }
        }
    }

  else if (outWord.compare("2") == 0 || outWord.compare("QUIT") == 0) {
    break;
}
else {
    cout << inWord << " is an unrecognized option, please try again" 
    << endl;
}
}  
while (outWord.compare("2") || outWord.compare("QUIT")); 
return 0;
}

Answer 1

在您使用的所有地方出现的问题：

cin >> something;

新行字符仍保留在cin中，以便您接下来阅读的内容。只要你每次读完一行，就写一下

string trash;
getline(trash, cin);

像：

cin >> something;
string trash;
getline(trash, cin);

然后新行字符将不会保留在cin中，您将从一个新线开始。

不停止，清除cin创建无限循环

1 个答案: