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map to function via pointer.

Sep 16, 2015 at 3:46am
spex (2)
i'm have a hard time with a map that is passed to a function and then adding to that map, for whatever reason my book doesn't seem to cover this.

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 #include <map>
#include <iostream>
#include <string>
#include <stdio.h>

using namespace std;

void register_user ( map<string, string> *name_to_password );

string logged_in ()
{
    cout << "you're logged in!" ;
    while ( 1 )
        {

        string input;
        getline( cin, input, '\n' );
        cout << "Menu:" << endl << "1.change password" << "2.log out" ;
        getline( cin, input, '\n' );

        if ( input == "1" )
            {
            string new_password;
            cout << "Enter new password: ";
            cin >> new_password;


            cout << "New password has been set!";
            return new_password;


            }
        else if ( input == "2" )
            {
            cout << "you are now logged out!" << endl;
            break;
            }
        else
            {
            cout << "You must enter from one of the options in the menu " << endl;
            }
        }

}

void register_user ( map<string, string> *name_to_password )
{
    while ( 1 )
    {
        string username;
        cout << "To register we're going to need a user name...: " << endl;
        cin >> username;
        map<string, string>::iterator itfind = name_to_password->find( username );
        if ( itfind != name_to_password->end() )
            {
            cout << "sorry bud! that username has been taken. try another!" << endl << endl;
            }
        else
        {
            cout << "type in your password: " << endl;
            string password;
            cin >> password;
// this is where i'm getting an error, i've tried "*"before name_to_password.
            name_to_password[ username ] = password;
            cout << endl << "Register Successful! " << endl << endl;
            break;
        }
    }
}

int main ()
{

    map<string, string> name_to_password;
    name_to_password[ "danny" ] = "ramonesgghey1";

    int breaker = 1;

    while ( breaker == 1 )
    {
        string input;
        cout << "what would you like to do? ";
        cout << "1.log in" << "2.register";
        cin >> input;

        if ( input == "1" )
            {
                    string user_name_login;
                    getline( cin, user_name_login, '\n' );
                    cout << "enter your username: ";
                    getline( cin, user_name_login, '\n' );
                    map <string, string>::iterator itfind = name_to_password.find ( user_name_login );
                    if ( itfind != name_to_password.end() )
                    {
                        string password;
                        cout << "Enter password to log in: ";
                        cin >> password;
                        string map_password = itfind->second;
                        if ( map_password == password )
                        {
                        itfind->second = logged_in ();
                        }
                        else
                        {
                            cout << "wrong password entered!" ;
                        }
                    }
                    else if ( itfind == name_to_password.end() )
                    {
                        cout << "there is no entry with that username" ;

                    }
            }

        else if ( input == "2" )
            {
            register_user ( &name_to_password );
            }
        else
            {
                cout << "you must enter from one of the options in the menu: " ;
            }
    }
}
Edit & run on cpp.sh
Sep 16, 2015 at 3:52am
Renthalkx97 (152)
You need to dereference the name_to_password inside of parentheses.

(*name_to_password)[username]
Last edited on Sep 16, 2015 at 3:52am
Sep 16, 2015 at 8:09am
coder777 (8442)
You may consider to pass it as a reference:

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void register_user ( map<string, string> &name_to_password ) // Note: &
{
...
        map<string, string>::iterator itfind = name_to_password.find( username ); // Note: . instead of ->
...
            name_to_password[ username ] = password;
...
}
Sep 16, 2015 at 8:48am
spex (2)
Renthalkx97
Thanks that seemed to do the trick.

Coder777
Reference does seem like the better option but it's good to know both ways, isn't it ?

Thanks again guys.
Sep 16, 2015 at 8:55am
Renthalkx97 (152)
It's personal preference really. Pointers and references basically both do the same exact thing except you can't reassign references like you can pointers.
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