c++ - C++ 文件打开

Question

我是 C++ 的新手，我想练习打开文件和输入文本，现在我意识到这是存储登录信息的最糟糕的方式，但这正是我选择模拟它的方式，至少它不会完全随机。现在我在所有方面都做得很好，除了一个地方似乎我一直在出错整个代码是

#include <iostream>
#include <string>
#include <fstream>
#include <new>
using namespace std;
string login() {
    string username, password;
    cout << "What is your username?\n";
    cin >> username;
    cout << "What is your password, " << username << endl;
    cin >> password;
    //Verify info
    return username;
}
string signup() {
    string username, password, cpass, bio;
    do {
        cout << "What is your username?\n";
        cin >> username;
        cout << "What is your password?\n";
        cin >> password;
        cout << "Confirm password: ";
        cin >> cpass;
        cout << "Describe what you like to do:\n";
        cin >> bio;
    } while (password != cpass);
    ofstream user = new ofstream();
    user("users.txt");
    if (user.is_open()) {
        //Make sure the program is writing to the end of the file!
        user.seekp(0,std::ios::end);
        user << username << endl;
        user << password << endl;
        user << bio << endl;
    } else {
        cout << "Something went wrong with opening the file!";
    }
    user.close();
    return username;
}
int main() {
    string answ;
    cout << "Hello, welcome to wewillscamyou.net, are you already signed up?\n";
    if(answ == "Yes" || answ == "yes") {
        string username = login();
    } else {
        string username = signup();
    }
    return 0;
}

但我在这两行出现错误，这不是因为打字错误，我需要帮助，因为这在 java 中可以工作:

ofstream user = new ofstream();
user("users.txt");

Answer 1

C++ 中的 Buddy new 用于创建动态分配 对象，或者您有指针指向的对象，或者您必须为其分配内存的对象。通常是指向对象的指针。

class A {
    public:
        A() { }
};

int main () {
    A a (); // object (created as value)
    A *a = new A(); // notice pointer, I need to allocate memory for it thus I have to use `new`
}

结论 new 在 C++ 中意味着为这个对象分配足够的内存并给我它的地址。因此，要解决您的错误，您有多种选择:

ofstream user ("user.txt");

或

ofstream user;
user = ofstream("users.txt");

或

ofstream user;
user.open("user.txt");
...
user.close("user.txt");
user("users.txt");