Question

我目前正在开发一个库程序，特别是从文本文件中删除一本书。这是有问题的功能：

void deleteBook(){

ifstream fin;
ofstream fout;

int fileLength = 0;
bool bookExist, looper = false, looper2 = false;
string isbn, author, title, checkOutDate, dueDate, answer, fileLine, isbnCurrent;

while (looper == false){      //Loop to ensure user inputs a valid book

  cout << endl << "Enter the Isbn of the book you would like to delete: ";      //isbn determines book
     cin >> isbn;

  bookExist = isBookExist(isbn);

  if (bookExist == true){
     looper = true;
  }
  else{
     cout << endl << "The book you have entered does not exist in the system, please try again" << endl;
  }
}

getBookInfo(isbn, author, title, checkOutDate, dueDate);    //Retrieves data about book and displays

cout << endl << "The isbn of the book is: " << isbn;
cout << endl << "The author of the book is: " << author;
cout << endl << "The title of the book is: " << title;
cout << endl << "The check out date of the book is: " << checkOutDate;
cout << endl << "The due date of the book is: " << dueDate;

while (true){

cout << endl << "Are you sure you would like to delete this book? (Enter 'yes' or 'no'): ";
  cin >> answer;

  if (cin.fail()){     //This most likely wont come up under any circumstances, but is here for completion
     cout << "Your answer was not valid, please try again." << endl;
  }

  if ((answer.compare("yes") == 0) || (answer.compare("Yes") == 0)){

     fin.open(booksFile);       //open books file and a temporary
     fout.open("tempBook.txt");

     while (getline(fin, fileLine))   //Check how long file is
        fileLength++;

     fin.close();         //reset book file
     fin.open(booksFile);

     while (looper2 == false){

        for (int i = 0; i < fileLength; i += 5){

           getline(fin, isbnCurrent);             //Go through file and look for book in question

           if (isbn == isbnCurrent){

              fout << " " << endl << " " << endl << " " << endl << " " << endl << " ";
              looper = true;    //If book is found, set all fields to empty
              break;

           }

           getline(fin, author);      //If not, continue through file
           getline(fin, title);
           getline(fin, checkOutDate);
           getline(fin, dueDate);

           fout << isbn << endl << title << endl << author << endl << checkOutDate << endl << dueDate << endl;
           //Outputs data back onto file
        }


     fin.close();
     fout.close();

     remove("books.txt");    //sets book file to the temp
     rename("tempBook.txt", "books.txt");
  }
  } else if ((answer.compare("no") == 0) || (answer.compare("No") == 0)){
     break;      //Leave function if user decides not to delete
  }
  else 
     cout << "Input invalid, please enter either 'yes' or 'no' " << endl;
  }
}

该程序似乎一直工作到yes / no部分。此时输入没有按预期工作，但输入yes无效，程序只是静止不动。我不完全确定问题出在哪里，尽管booksFile的格式如下：

ISBN 标题作者入住日期退房日期

提前致谢！

Answer 1

在你的内在while循环中你有：

while (looper2 == false) { ... }

但是，在该循环中，您没有将lopper2设置为true（您将lopper设置为true。）

顺便说一句：考虑一下whiles的使用方式，您是否考虑过使用break代替looper变量？例如，第一种情况就像这样清洁：

while (true)
{
    cout << endl << "Enter the Isbn of the book you would like to delete: ";determines book
    cin >> isbn;

    if (isBookExist(isbn))
        break;

    cout << endl << "The book you have entered does not exist in the system, please try again" << endl;
}

输入未注册

1 个答案: