C++ Can'；t读取文件并存储在结构的数据成员中

这是用于赋值的，所以我遵循所需结构布局的赋值准则以及重载。试图让我的程序读取每一行并将每一行分配给变量

文本文件如下所示：

John 

S

Maggey

G

#include "iostream"
#include "fstream"
namespace
{
    char buffer[1024];
    int allocated = 0;
}

//====================================================================
struct student
{
    char *firstname;
    char lastname;
    int studentId;
    int occupied;

    student() : lastname(0), studentId(0), occupied(0)
    {
        firstname = new char[64];
        for (int i = 0; i < 64; ++i)
            firstname[i] = 0;
    }

    student(int s)
    {
        std::cout << "constructor" << std::endl;
        std::cout << "Allocated: " << allocated << std::endl;
        int currentLoc = allocated;
        allocated += s;
        firstname = new (&buffer[currentLoc]) char[s];
        for (int i = 0; i < 64; ++i)
            firstname[i] = 0;
    }

    void *operator new(size_t s)
    {
        std::cout << "Operator new allocated: " << allocated << std::endl;
        int currentLoc = allocated;
        allocated += s;
        return &buffer[currentLoc];
    }

    void student::operator delete(void *ptr)
    {
        std::cout << "Delete called " << std::endl;
        std::free(ptr);
    }

    student::~student()
    {
    }
};

//====================================================================
int main(int argc, char** argv)
{
    student *studentLoader = new student[25];

    std::fstream fin;
    fin.open("students.txt");
    char ln;
    for (int i = 0; i < 25; ++i)
    {
        fin.getline(studentLoader[i].firstname, 99);
        fin.getline(ln, 64);
        studentLoader[i].lastname = ln;
        studentLoader[i].studentId = (rand() % (9999 - 999)) + 999;
        studentLoader[i].occupied = 1;
        if ((i % 10) == 0)
        {
            std::cout << "First name: " << studentLoader[i].firstname << " Last initial: " << studentLoader[i].lastname << " ID: " << studentLoader[i].studentId << std::endl;
            delete[] studentLoader;
        }
    }
    fin.close();

    return 0;
}

我的代码如下所示：

John 

S

Maggey

G

#include "iostream"
#include "fstream"
namespace
{
    char buffer[1024];
    int allocated = 0;
}

//====================================================================
struct student
{
    char *firstname;
    char lastname;
    int studentId;
    int occupied;

    student() : lastname(0), studentId(0), occupied(0)
    {
        firstname = new char[64];
        for (int i = 0; i < 64; ++i)
            firstname[i] = 0;
    }

    student(int s)
    {
        std::cout << "constructor" << std::endl;
        std::cout << "Allocated: " << allocated << std::endl;
        int currentLoc = allocated;
        allocated += s;
        firstname = new (&buffer[currentLoc]) char[s];
        for (int i = 0; i < 64; ++i)
            firstname[i] = 0;
    }

    void *operator new(size_t s)
    {
        std::cout << "Operator new allocated: " << allocated << std::endl;
        int currentLoc = allocated;
        allocated += s;
        return &buffer[currentLoc];
    }

    void student::operator delete(void *ptr)
    {
        std::cout << "Delete called " << std::endl;
        std::free(ptr);
    }

    student::~student()
    {
    }
};

//====================================================================
int main(int argc, char** argv)
{
    student *studentLoader = new student[25];

    std::fstream fin;
    fin.open("students.txt");
    char ln;
    for (int i = 0; i < 25; ++i)
    {
        fin.getline(studentLoader[i].firstname, 99);
        fin.getline(ln, 64);
        studentLoader[i].lastname = ln;
        studentLoader[i].studentId = (rand() % (9999 - 999)) + 999;
        studentLoader[i].occupied = 1;
        if ((i % 10) == 0)
        {
            std::cout << "First name: " << studentLoader[i].firstname << " Last initial: " << studentLoader[i].lastname << " ID: " << studentLoader[i].studentId << std::endl;
            delete[] studentLoader;
        }
    }
    fin.close();

    return 0;
}

---

变量中不会插入任何内容

如果这不是打字错误，并且您确实希望使用单个字符作为

姓氏

，那么您也应该将其作为单个字符阅读：

fin>>studentLoader[i].lastname>>std:：ws

---

还考虑使用函数和类的阅读。这通常是一个好习惯，可以避免大量的失败。

通过稍微修改您的

struct student

，将

firstname

和

lastname

的类型更改为

std:：string

，您将不必动态分配/取消分配内存，代码将减少一半

例如，您可以将其定义为：

struct student {

    // constructor
    student (std::stirng fn, std::stirng ln, int ID, int oc) 
       :  firstname(fn), lastname(ln), studentID(ID), occupied(oc) { }

    // data members
    std::string firstname;
    std::string lastname;  
    int studentID;
    int occupied;
}; 

然后要从文件中读取并存储在

struct student

，可以使用

std:：vector

，如下所示：

#include <iostream>
#include <string>
#include <vector>
#include <sstream> 

int main () {
    // stores all elements created from the reading of the file 
    std::vector<student> class_of_students;

    // attach an input stream
    std::ifstream fin("students.txt");
    // check if file successfully opened 
    if (!fin) std::cerr << "Can't open input file!\n";

    // line of text
    std::string line;

    // read file line by line
    while (getline(fin, line)) {
         // stream to extract data from a line
         std::stringstream ss(line);

         // input variables
         std::string first_name;
         std::string last_name;
         int ID;
         int occupied;

         // example that assumes line format: "f_name l_name ID occ"
         while (ss >> first_name >> last_name >> ID >> occupied) {

             // store one element of type student to the vector
             class_of_students.emplace_back(student(first_name, last_name, ID, occupied));
         }
    }
}

#包括
#包括
#包括
#包括
int main（）{
//存储读取文件时创建的所有元素
std：：向量类学生；
//附加输入流
std：：ifstream fin（“students.txt”）；
//检查文件是否成功打开
如果（！fin）std:：cerr>名字>>姓氏>>ID>>已占用）{
//将student类型的一个元素存储到向量
学生的班级。返回（学生（名字、姓氏、ID、占用））；
}
}
}

更多关于和的使用

注:

---

此外，当您生成学生ID时，您需要它不仅是随机的，而且是唯一的。

请使用

std:：string

而不是

char*

。另外，请不要使用

new

delete

。您应该检查并删除任何不必要的代码（如

new

和

delete

重载运算符）。这是一项作业，因此我遵循要求。我们需要重载这些运算符以及使用char*。您可以从明智地缩进代码开始，这样代码实际上是可读的。为了看起来更好，进行了编辑，添加了关于我为什么使用char*以及重载new和delete运算符的说明。