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While循环不读取整个ifstream文件

fileinputstream c++

-1

mahmoudalsof · 技术社区 · 6 年前

函数(或者while循环)正在读取前两条记录,然后退出循环。它正在正确读取所有内容,但为什么它不继续读取整个文件(其中有13条记录)?

我试过了 while(!infile.eof())

这是我的ReadFile块:

void ReadFile() {// Reads data file into array

    ifstream infile;

    infile.open(cTextFileName);

    if (!infile.good()) {
        cout << "Cant find text data file!" << endl;
        exit(1);
    }

    int i = 0;
    int status;
    //bool endOfFile = infile.eof();

    infile >> gRecs[i].StudentNo;

    while (infile) {
        infile >> gRecs[i].FirstName;
        infile >> gRecs[i].LastName;
        infile >> gRecs[i].NumSubjects;
        //cout << "ENTERED WHILE LOOP" << endl;

        for (int j = 0; j < gRecs->NumSubjects; j++) {
            infile >> gRecs[i].Subjects[j].Code;
            infile >> status;

            if (status == 0) {
                gRecs[i].Subjects[j].Status == eEnrolled;
            } else if (status == 1) {
                gRecs[i].Subjects[j].Status == eProvisional;
            } else {
                gRecs[i].Subjects[j].Status == eWithdrawn;
            }


            infile >> gRecs[i].Subjects[j].Mark;

        }

        i++;
        infile >> gRecs[i].StudentNo;
    }

    gNumRecs = i;
    infile.close();
    infile.clear();

    cout << gNumRecs << " Records read!" << endl;
}

2 回复 | 直到 6 年前

Hugo Maxwell 6 年前

for (int j = 0; j < gRecs->NumSubjects; j++) {

应该是

for (int j = 0; j < gRecs[i].NumSubjects; j++) {

Jerry Coffin 6 年前

在我看来,解决这个问题的最好办法就是完全避免它。

我将编写一个只读取一条记录的函数,而不是试图读取整个文件的单个函数。然后重复调用该函数,直到读取了整个文件。为了适应标准库其余部分的工作方式,应该将读取单个记录的函数命名为 operator>> . 它应该会收到一份推荐信 istream 以及对记录的引用,并返回对 峡流 当它完成的时候。

std::istream &operator>>(std::istream &is, gRec &record) {
    is >> record.FirstName;
    is >> record.LastName;
    is >> record.NumSubjects;
    for (int i=0; i<record.NumSubjects; i++) {
        is >> record.subjects[i].code;

        int raw_status;
        is >> raw_status;
        record.subject[i].status = cvt_status(raw_status);
        is >> record.mark;
    }
    return is;
}

Status , Subject 和 Schedule ,每个都定义了自己的 操作员>&燃气轮机; 要从文件中读取自身,请执行以下操作:

class Status {
    enum class status { enrolled, provisional, withdrawn } s;

    friend std::istream &operator>>(std::istream &is, Status &s) { 
        int i;
        is >> i;
        switch (i) { 
            case 1: s.s = status::enrolled;    break;
            case 2: s.s = status::provisional; break;
            case 3: s.s = status::withdrawn;   break;
        }
        return is;
    }
};

class Subject {
    int code;
    Status status;
    int mark;
public:
    friend std::istream &operator>>(std::istream &is, Subject &s) { 
        return is >> s.code >> s.status >> s.mark;
    }
};

class Schedule {
    std::vector<Subject> classes;
public:
    friend std::istream &operator>>(std::istream &is) {
        int num;
        is >> num;
        for (int i=0; i<num; i++) {
            Subject temp;
            is >> temp;
            classes.push_back(temp);
       }
       return is;
    }
};

那么一张唱片应该是这样的:

class Record {
    std::string FirstName, LastName;
    Schedule classes;
public:
    std::istream &operator>>(std::istream &is, Record &r) {
        return is >> r.FirstName >> r.LastName >> r.classes;
    }
};

最后,阅读一个完整的学生档案是这样的:

std::ifstream infile("filename");
std::vector<Record> records{std::istream_iterator<Record>(infile), {}};