有没有办法添加用户使用 C++ 输入的行数？

Question

我尝试使用动态字符串数组来制作它，但是当我尝试添加 2 行时，它只添加了 1 行，我不知道为什么 这是我的代码

#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main()
{
    int x;
    string name;
    string* lines;
    cout << "Input the file name to be opened : ";
    cin >> name;
    cout << endl << "Input the number of lines to be written : ";
    cin >> x;
    lines = new string[x];
    cout << endl << "The lines are :";
    for (int i = 0; i < x; i++)
    {
        getline(cin,lines[i]);
    }
    fstream File(name, ios::out | ios::app);
    for (int i = 0; i < x; i++)
    {
        File << lines[i] << endl;
    }
    File.close();
}

它给了我这个警告： C6385 从 'lines' 读取无效数据：可读大小为 '(unsigned int)*28+4' 字节，但可能读取 '56' 字节

Answer 1

要存储您的字符串，您可以使用std::vector，它是一个可变大小的 C++ 容器，比 C 类型数组更受欢迎，下面是 cmets 的示例：

Live sample

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <limits>

using namespace std; //for test purposes, in real code you shoud use std:: scope

int main()
{
    int x;
    string name, line;
    vector<string> lines; //container

    cout << "Input the file name to be opened : ";
    cin >> name;

    fstream File(name, ios::app | ios::out);

    cout << endl
         << "Input the number of lines to be written : ";
    cin >> x;
    cin.ignore(numeric_limits<streamsize>::max(), '\n'); //needed because getline does not ignore new line characters
                                                         //explicitly looking to clear buffer till '\n', improves clarity
    cout << endl
         << "The lines are :";

    while (x > 0)
    {
        getline(cin, line);
        lines.push_back(line); //add lines to vector, this is assuming you need the lines in memory
        x--;                   //otherwise you could save them directly to the file
    }

    if (File.is_open())
    {
        for (string s : lines)  //writing all the lines to file
        {
            File << s << endl;
        }
        File.close();
    }
}