How do I create a file with as name the players username?

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Hello,

I tried to create a test login program.
(I know this isn't safe but I'm trying to create some things to learn).
This line gives an error: file.open(username + ".txt");
I think the + in that line doesn't work but I'm not sure.

This is the error:
c:\program files (x86)\codeblocks\mingw\bin\..\lib\gcc\mingw32\4.7.1\include\c++\fstream|702|note: void std::basic_ofstream<_CharT, _Traits>::open(const char*, std::ios_base::openmode) [with _CharT = char; _Traits = std::char_traits<char>; std::ios_base::openmode = std::_Ios_Openmode]|

This is the code:

C++

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

using namespace std;

enum MainProgramParts{ SUCCESS, FAILED, STOP, OPTIONS };
MainProgramParts options();
MainProgramParts success();
MainProgramParts failed();

int main()
{
        MainProgramParts nextPart = OPTIONS;

        while(nextPart != STOP){
        switch(nextPart){
        case OPTIONS:
            nextPart = options();
            break;
        case SUCCESS:
            nextPart = success();
            break;
        case FAILED:
            nextPart = failed();
            break;
        }
    }
}

MainProgramParts options(){
    int choice;

    cout << "1: Register" << endl;
    cout << "2: Login" << endl << endl;
    cin >> choice;

    if(choice == 1)
    {
        string username;
        string password;

        cout << "Username: ";
        cin >> username;
        cout << "Password: ";
        cin >> password;

        ofstream file;
        file.open(username + ".txt");
        file << username << endl << password;
        file.close();

        main();

    if(choice == 2)
    {
    string username;
    string password;
    string un;
    string pw;

    cout << "Username: ";
    cin >> username;
    cout << "Password: ";
    cin >> password;

    ifstream read(username + ".txt");
    getline(read, un);
    getline(read, pw);

    if(un == username && pw == password)
    {
        return SUCCESS;
    }
    else
    {
        return FAILED;
    }
}
}
}

MainProgramParts success(){
    cout << "Successfully logged in!";
}

MainProgramParts failed(){
    cout << "Incorrect password / username!";
}

Thanks,
~Steff

Posted 18-Aug-15 7:17am

Member 11918147

Updated 18-Aug-15 7:23am

v3

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Comments

jeron1 19-Aug-15 11:51am

As an aside, don't call main() explicitly, like you are in the options() function.

2 solutions

Solution 1

No, this is not the concatenation, which is a valid std::string operator: http://www.cplusplus.com/reference/string/string/operator+[^].

The problem is the type, as the expected argument type is old lame char*. Use the c_str operation to get a "C string" out of your std::string instance: http://www.cplusplus.com/reference/string/string/c_str[^].

—SA

Posted 18-Aug-15 11:48am

Sergey Alexandrovich Kryukov

Updated 18-Aug-15 11:49am

v2

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User 59241 · Accepted Answer · 2015-08-18T19:48:00

SA is correct.

You may find it better to use visual-studio-community[^]. At least take a look at it.

Your code would then work fine because VSC is C++11 compliant.

Passing a std::string to open() is allowed in C++11. You may simply concatenate the two std::strings making your file name using the + operator.

C++

file.open(username + ".txt");

In other compilers you will have to pass a char* (C string). You may use c_str() to get a C string from a std::string after concatenating the two strings.

C++

file.open((filename + ".txt").c_str());