如何在 C++ 中保留文本文件的内存？

Question

最近，我写了一个形状生成器项目，用C++显示三角形和矩形的形状。输出将显示在屏幕和文本文件中。但是我有一个问题，我如何让文本时间记住用户选择的所有形状？例如，形状总是存储在文本文件中。如果第一次运行我选择了 3 次 ..当我下次选择 2 次时退出 program.the 时，这 3 个选定的对象应该保留在文件中…然后退出程序。文本文件总共应该有 5 个对象。

这是我的代码：

#include <iostream>
#include <fstream>
#include <conio.h>

using namespace std;

void printTriangle(int n)
{
    cout << "\t~~Triangle Generator~~" << endl;
    cout << "\n\tEnter Height of Triangle: ";
    cin >> n;
    int k = 2 * n - 2;
    cout << "\n";
    // open a file in write mode.

    ofstream outfile;
    outfile.open("shape_generator.txt");

    // character to be printed
    char ch = 'O';

    // outer loop to handle number of rows
    // n in this case
    for (int i = 0; i < n; i++) {

        // inner loop to handle number spaces
        // values changing acc. to requirement
        for (int j = 0; j < k; j++) {
            cout << " ";
            outfile << " ";
        }

        // decrementing k after each loop
        k = k - 1;

        // inner loop to handle number of columns
        // values changing acc. to outer loop
        for (int j = 0; j <= i; j++) {
            // printing stars
            cout << ch << " ";
            outfile << ch << " ";
        }

        // ending line after each row
        cout << endl;
        outfile << "\n";
    }
    cout << "\n";
}

void printRectangle(int height, int width)
{

    cout << "\t~~Rectangle Generator~~" << endl;
    int i, j;
    /* Input number of rows from user */
    cout << "\n\tEnter Height of Rectangle: ";
    cin >> height;
    cout << "\n\tEnter Width of Rectangle : ";
    cin >> width;
    cout << "\n";
    // open a file in write mode.
    ofstream outfile;
    outfile.open("shape_generator.txt");

    /*Iterate through N rows*/
    for (i = 1; i <= height; i++) {
        /*Iterate over columns*/
        for (j = 1; j <= width; j++) {
            /*Print star for each column*/
            cout << "O";
            outfile << "O";
        }

        /* Move to the next line/row */
        cout << "\n";
        outfile << "\n";
    }
    cout << "\n";
    // close the opened file.
    outfile.close();
}

void exit()
{
    cout << "\n\tThank You For Using Our Services. Have A Nice Day!" << endl;
}

int main()
{
    int n;
    int height;
    int width;
    int option;

    do {
        system("color ED");
        cout << "\t" << string(35, '_') << "\t\n";
        cout << "\n\tWelcome to Shape Generator Service!\n";

        cout << "\t" << string(35, '_') << "\t\n\n";
        cout << "\t* * * * * * * * * * * * *" << endl;
        cout << "\t*                       *" << endl;
        cout << "\t*\t1.Triangle \t*" << endl;
        cout << "\t*                       *" << endl;
        cout << "\t*\t2.Rectangle\t*" << endl;
        cout << "\t*                       *" << endl;
        cout << "\t*\t0.Exit     \t*" << endl;
        cout << "\t*                       *" << endl;
        cout << "\t* * * * * * * * * * * * *" << endl;
        cout << "\n\tEnter Option: ";
        if (cin >> option) {
            switch (option) {
            case 1:
                system("cls");
                system("color D7");
                printTriangle(n);
                break;

            case 2:
                system("cls");
                system("color CF");
                printRectangle(height, width);
                break;

            case 0:
                exit();
                break;

            default:
                cout << "\nThe Option is Not Available! Please Try Again.\n" << endl;
                break;
            }
        }
        else {
            cout << "Only Digits are Allowed! Press any key to continue..." << endl;
            getch();
            cin.clear();
            cin.ignore();
            option = 15;
        }

    } while (option != 0);
}

Answer 1

因为你正在写一个文本文件并且有 #include <fstream 那么我认为你的意思是用附加打开文件，比如：

（例子）

#include <iostream>
#include <fstream>

using namespace std;

int main(){
    fstream file; //open the file
    file.open("shapes.txt", fstream::out|fstream::app); //set mode as output and append
    string phrase = "Example!\n\n"; //example phrase
    file << phrase;
}

因为：

-fstream::app 是附加的，基本上会在文件末尾添加新内容而不删除其他内容

-fstream::out 是输出，基本上意味着您要放置一个输出，追加是一个输出

-file <<基本上会在文件中添加以下参数

如何在 C++ 中保留文本文件的内存？

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