使用流写入文件内部

Using of stream to write inside file

本文关键字：文件 内部      更新时间：2023-10-16

我应该在一个名为"mydata.txt"的文件中打印（x，y）值。但是由于某种原因，我收到以下错误消息："错误：无法打开输出文件 mydata.txt" 我不确定程序是应该创建文本文件还是应该创建文件。我尝试了后者，但仍然不起作用。这是我的代码： 

#include "std_lib_facilities_5.h"
class Point{
    public:
    int x;
    int y;
    // Coordinate members x and y
    Point(int nn = 0 , int mm = 0): x(nn), y(mm){}
    friend ostream& operator<< (ostream &out, const Point &point);
};
ostream& operator<<(ostream& os, const Point& point){
    os << point.x << " " << point.y;
    return os;
}
int main()
try {
    int x1, x2;
    vector<Point> original_points;
    for(int i = 0; i < 7; ++i) {
        cout << "Please input coordinate points as (x,y): ";
        cin >> x1 >> x2;
        original_points.push_back(Point(x1,x2));
    }
    for(int i = 0; i < 7; ++i){
        cout << "Original points: " << original_points[i] << endl;
    }
    string outputFile = "mydata.txt";
    ofstream ost {"mydata.txt"};
    ost.open(outputFile,ofstream::out);
    if(!ost) error("can't open output file ", outputFile);
    for(int i = 0; i < original_points.size(); ++i){
        ost << original_points[i] << " " << original_points[i];
    }
    ost.close();
}
catch (exception& e) {
    cerr << "error: " <<e.what() << 'n';
    return 1;
    }
    catch (...) {
        cerr << "Oops: unknown exception!n";
        return 2;
    }

这是我运行它时的输出：

Please input coordinate points as (x,y): 1 2
Please input coordinate points as (x,y): 1 1 
Please input coordinate points as (x,y): 2 2 
Please input coordinate points as (x,y): 3 3 
Please input coordinate points as (x,y): 4 4 
Please input coordinate points as (x,y): 5 5 
Please input coordinate points as (x,y): 6 6
Original points: 1 2
Original points: 1 1
Original points: 2 2
Original points: 3 3
Original points: 4 4
Original points: 5 5
Original points: 6 6
error: can't open output file mydata.txt
Program ended with exit code: 1

ofstream ost {"mydata.txt"};打开文件。

然后，您尝试在下一行中再次打开它失败，因为它已经打开了。
删除第二行。

在你ost.close();删除行 - 析构函数会在需要的时候为你关闭它。

试试这个

    #include "std_lib_facilities_5.h"
class Point{
    public:
    int x;
    int y;
    // Coordinate members x and y
    Point(int nn = 0 , int mm = 0): x(nn), y(mm){}
    friend ostream& operator<< (ostream &out, const Point &point);
};
ostream& operator<<(ostream& os, const Point& point){
    os << point.x << " " << point.y;
    return os;
}
int main()
try {
    int x1, x2;
    vector<Point> original_points;
    for(int i = 0; i < 7; ++i) {
        cout << "Please input coordinate points as (x,y): ";
        cin >> x1 >> x2;
        original_points.push_back(Point(x1,x2));
    }
    for(int i = 0; i < 7; ++i){
        cout << "Original points: " << original_points[i] << endl;
    }
    ofstream ost;
    ost.open("mydata.txt");
    if(!ost) error("can't open output file ", "mydata.txt");
    for(int i = 0; i < original_points.size(); ++i){
        ost << original_points[i] << " " << original_points[i];
    }
    ost.close();
}
catch (exception& e) {
    cerr << "error: " <<e.what() << 'n';
    return 1;
    }
    catch (...) {
        cerr << "Oops: unknown exception!n";
        return 2;
    }
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