Question

从txt文件导入一些数据时遇到问题。

.txt文件中的格式化文件数据为：

（int int double）例如（16 21 18.0）

我已经创建了一个从文件中获取数据的函数，它可以工作，但它只是给我第一行（即第一个读取对象），然后它返回0，没有错误。我想输入循环有问题，但我无法理解哪个问题。我应该导入存储在txt文件中的所有50个值（50行和1列）。提前谢谢。

Header3.h

#pragma once

struct Reading
{
    int day, hour;
    double temperature;
    char ch1, ch2;
    Reading();
    Reading(char c1, int d, int h, double t, char c2);
};

istream& operator>>(istream& is, Reading& r);   // Setting helper input function
ostream& operator<<(ostream& os, const vector<Reading>& r);  // Setting helper output function
void vec_import(vector<Reading>& v);   // Read data from txt file

temp_stats.cpp（header3的源文件）

#include "stdafx.h"
#include "std_lib_facilities.h"
#include "Header3.h"

void vec_import(vector<Reading>& v)
{
    string iname;
    cout << "Type input filename: ";
    cin >> iname;

    ifstream ist{ iname };
    if (!ist) error("Cannot read from filename ", iname);

    while (true)
    {
        Reading r;
        ist >> r;
        if (!ist) break;
        v.push_back(r);
    }
}

Reading::Reading()
    :ch1{ ' ' }, day{ 0 }, hour{ 0 }, temperature{ 0 }, ch2{ ' ' } {};

Reading::Reading(char c1, int d, int h, double t, char c2)
    :ch1{ c1 }, day{ d }, hour{ h }, temperature{ t }, ch2{ c2 } {};

istream& operator>>(istream& is, Reading& r)
{
    int d, h;
    double t;
    char c1;
    char c2;

    is >> c1;
    switch (c1) 
    {
    case '(':
        break;
    default:
        break;
        return is;
    }

    is >> d >> h >> t;

    is >> c2;
    switch (c2)
    {
    case ')':
        break;
    default:
        break;
        return is;
    }

    r = Reading(c1, d, h, t, c2);

    return is;

}

ostream& operator<<(ostream& os, const vector<Reading>& r)
{
    for (int i = 0; i < r.size(); ++i)
    {
        return os << r[i].ch1 << " " << r[i].day << " " << r[i].hour
            << " " << setprecision(1) << fixed << r[i].temperature
            << " " << r[i].ch2 << endl;
    }
}

的main.cpp

// Temperature Reading 2.0.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "std_lib_facilities.h"
#include "Header3.h"


int main()
{
    Reading r;
    vector<Reading> v;
    vec_import(v);
    cout << v;

    keep_window_open();

    return 0;
}

Txt文件：

Answer 1

您的问题是operator<<()。您将立即从循环返回，因此它只打印一个值。修复：

ostream& operator<<(ostream& os, const vector<Reading>& r)
{
    for (int i = 0; i < r.size(); ++i)
    {
        os << r[i].ch1 << " " << r[i].day << " " << r[i].hour
            << " " << setprecision(1) << fixed << r[i].temperature
            << " " << r[i].ch2 << endl;
    }
    return os;
}

无法导入所有txt文件数据

1 个答案: