Question

我正在制作电话簿，并且到目前为止已经成功地让用户输入他们的信息，将其保存为字符串，将字符串保存到文件，并使用关键字搜索该字符串。但是，它仅对输入的第一个接触有效。输入新联系人时，它会覆盖保存在文件中的上一个字符串。如何将其打印到下一行，并开发可以搜索的联系人列表。任何帮助深表感谢。这是我的代码：

#include <iostream>
#include <string>
#include <ostream>
#include <fstream>

using namespace std;

struct person
{
    string Name;
    string Address;
    string PhoneNumber;
    string Email;
};

int main()
{
ResetUserSelection:
    vector<person>ContactList;

    int userselection = 0;

    cout << "Press 1 to Add Contact" << endl;
    cout << "Press 2 to Search for Contact"<<endl;
    cout << "What do you want to do? ";
    cin >> userselection;

    if(userselection == 1)
    {
        person newPerson;

        cout << endl;
        cin.ignore();
        cout << "What is your Name? " ;
        getline(cin,newPerson.Name);

        cout << "What is your Address? " ;
        getline(cin,newPerson.Address);

        cout << "What is your Phone Number? " ;
        getline(cin,newPerson.PhoneNumber);

        cout << "What is your Email? ";
        getline(cin,newPerson.Email);

        cout << endl;

        string fullContact = "Name: " + newPerson.Name + ", Address: " +     newPerson.Address + ", Phone Number: " + newPerson.PhoneNumber + ", Email: " +     newPerson.Email + "\n";

        cout <<fullContact;

        cout << endl;

        ofstream myfile;
        myfile.open ("contactlist.txt");
        myfile << fullContact;
        myfile.close();
        goto ResetUserSelection;

        goto ResetUserSelection;
    }
    else
    {
        string search;

        ifstream Myfile;
        Myfile.open ("contactlist.txt");
        cout << "Who do you want to search for?" << endl;
        cin >> search;
        cout << endl;

        ifstream myfile;
        myfile.open ("contactlist.txt");
        string contact;
        while(getline(myfile, contact))
        {
            if(contact.find(search) != string::npos)
            {
                cout << search << "'s contact info" << endl << contact << endl << endl;
            }
        }
        myfile.close();

        goto ResetUserSelection;
    }
}

Answer 1

这一行：@Path缺少第二个参数，模式，应为myfile.open ("contactlist.txt");

app表示打开追加。 I.E.添加到文件的末尾。

Answer 2

当您打开文件进行写入时，默认情况下将filepointer设置为文件的开头。您应该在打开文件时添加附加选项。

请参阅ofstream::open的API如何执行此操作：

myfile.open ("contactlist.txt", ofstream::out | ofstream::app);

Answer 3

首先，包括矢量，因为你正在使用它。现在，你面临这个问题，因为没有给std :: fstream :: open提供正确的参数，所以它会覆盖以前的内容。

替换

    myfile.open ("contactlist.txt");

带

    myfile.open ("contactlist.txt",std::fstream::out|std::fstream::app);

它应该有效。有关详细信息，请http://www.cplusplus.com/reference/fstream/fstream/open/

将多个字符串打印到文件

3 个答案: