Question

我发布了以下代码，我从输入文件中读取 - 在结构中存储信息 - 然后写入输出文件。我知道eof函数不是安全，因此必须使用getline函数来检查是否检测到文件末尾;但是，在这个特定的代码中，我无法使用getline函数，因此最终依赖于eof函数。因此，您是否可以建议替换eof函数，或者让我知道在尝试初始化结构数组时如何使用getline函数。我使用了两个星号符号来表示我想要使用getline函数的位置。

#include <iostream>
#include <fstream>

using namespace std;
//student structure
struct student
{
  char name[30];
  char course[15];
  int age;
  float GPA;
};

ifstream inFile;
ofstream outFile;

student getData();
void writeData(student writeStudent);
void openFile();

int main (void)
{
  const int noOfStudents = 3; // Total no of students
  openFile(); // opening input and output files

  student students[noOfStudents]; // array of students

  // Reading the data from the file and populating the array
  for(int i = 0; i < noOfStudents; i++)
  {
        if (!inFile.eof()) // ** This where I am trying to use a getline function.
            students[i] = getData();
        else
            break ;
  }


  for(int i = 0; i < noOfStudents; i++)
    writeData(students[i]);

  // Closing the input and output files
  inFile.close ( ) ;
  outFile.close ( ) ;

}

void openFile()
{
  inFile.open("input.txt", ios::in);
  inFile.seekg(0L, ios::beg);
  outFile.open("output.txt", ios::out | ios::app);
  outFile.seekp(0L, ios::end);

  if(!inFile || !outFile)
  {
    cout << "Error in opening the file" << endl;
    exit(1);
  }

}

student getData()
 {
  student tempStudent;
  // temp variables for reading the data from file

  char tempAge[2];
  char tempGPA[5];

  // Reading a line from the file and assigning to the variables
  inFile.getline(tempStudent.name, '\n');
  inFile.getline(tempStudent.course, '\n');
  inFile.getline(tempAge, '\n');

  tempStudent.age = atoi(tempAge);

  inFile.getline(tempGPA, '\n');
  tempStudent.GPA = atof(tempGPA);
  // Returning the tempStudent structure
  return tempStudent;
 }

void writeData(student writeStudent)
 {
  outFile << writeStudent.name << endl;
  outFile << writeStudent.course << endl;
  outFile << writeStudent.age << endl;
  outFile << writeStudent.GPA << endl;
 }

Answer 1

您想为您的学生类型写一个operator>>。类似的东西：

std::istream& operator>>(std::istream& in, student& s) {
  in >> s.age; // etc.
  return in;
}

然后允许你写：

int studentNo = 0;
students[maxStudents];
while (studentNo < maxStudents && (in >> students[studentNo]))
  ++studentNo;

Answer 2

为什么不这样写？

而不是

inFile.getline(tempStudent.name, '\n');
inFile.getline(tempStudent.course, '\n');
inFile.getline(tempAge, '\n');

你可以

while(inFile.getline(tempStudent.name, '\n'))
{
    inFile.getline(tempStudent.course, '\n');
    inFile.getline(tempAge, '\n');
    //do stuffs
}

在这种情况下避免使用eof

2 个答案: