c ++：将ofstream＆传递给函数以连续追加到.txt文件

Question

I am writing a program for class wherein I need to call a function multiple times from "main.cpp" which takes an ofstream as a parameter, and the function itself needs to append new data to the end of the .txt file every time it's called (in this example I've made the data of type int for simplicity's sake).

What's been happening is that when the function gets called multiple times in main, it just overwrites everything instead of appending new data to the end of the file. I know everything else in my program works so I'm just going to strip it down to the bare bones as much as possible so that this isn't TL;DR. I have included

#include<fstream>
using namespace std;

in all of my files.

Here's the gist of it:

in main.cpp:

aClass* someClass = new aClass;
int data = 0;
...
ofstream myfile ("file.txt");
someClass->appendData(myfile, data);
...

in aClass.h:

void appendData(ofstream& myfile, int data);

in aClass.cpp:

void aClass::appendData(ofstream& myfile, int data){
    if(myfile.is_open()){
        myfile << data << "\n";
        myfile.close();
    }
    else cout << "Couldn't open file";
}

If anyone could help me with this I'd appreciate it. For some reason they haven't had us touch fstreams in over a year and I'm not sure what the problem is here.

Answer 1

The call

myfile.close();

in appendData is not right. Any subsequent output operations on myfile are ignored.

Remove it from there.

You may add it in main but it is optional. The destructor will call close() . However, there is no harm if you call close() on the object if you are sure you are not going to use it to write into it any more