Void return?

[Hazukiy]

Hi, I'm trying to create a function that works in a way like a void, where you have to call it for it to execute but I found that you can't return in a void, here's what I was HOPING to do...

  void CallCommandRegister()
{
	//Register Username
	cout << "Please enter a username." << endl;
	cin >> sRegisterUsername;
	if ( sRegisterUsername.size() >= 20 )
	{
		cout << "Username can't be more than 20 characters long." << endl;
		return CallCommandRegister();
	}
	else if ( sRegisterUsername.size() <=5  ) 
	{
		cout << "Username can't be less than 5 characters long." << endl;
		return CallCommandRegister();
	}
	else 
	{
		cout << "Username: " << sRegisterUsername << " successful." << endl;
	}
}

[giblit]

You wouldn't return the function. You would just call the function again. Simply remove the return statement. What you are doing is called recursion.

http://www.cplusplus.com/forum/articles/2231/ ( these are calling with ints though )


But lets look at this example:

void output( int i )
{
    if( i == 5 )
        std::cout << "Hello world!" << std::endl;
    else if( i < 5 )
        output( i + 1 );
    else //i > 5
        output( i - 1 );
}


//another way to do the same function:

void ouptut( int i )
{
    if( i != 5 )
    {
        while( i < 5 )
            ++i;
        while( i > 5 )
            --i;
    }
    std::cout << "Hello world!" << std::endl;
}

Though these probably aren't the most practical examples but hopefully you get the idea.

[Hazukiy]

Ah ok I've got the return value working now.


I've done

//Register Username
	cout << "Please enter a username." << endl;
	cin >> sRegisterUsername;
	if ( sRegisterUsername.size() >= 20 )
	{
		cout << "Username can't be more than 20 characters long." << endl;
		return CallCommandRegister();;
	}
	else if ( sRegisterUsername.size() <=5  ) 
	{
		cout << "Username can't be less than 5 characters long." << endl;
		return CallCommandRegister();
	}
	else 
	{
		cout << "Username: " << sRegisterUsername << " successful." << endl;
	}

But the problem that I face now is how would I create sections within that void? So I have a Register username section and a Register password section within that void. Is there a way to split those sections up so that when I come to return an error I can do something like

 return RegisterUsername();

For the username and

 return RegisterPassword();

for the password.

[yulingo]

Well you could certainly write functions called RegisterUsername() and RegisterPassword() and call them from within your CallCommandRegister() function.

Instead of using recursion, you could use a while loop to keep asking the user for a username/password until successful:

// Asks the user to register a username and checks to make sure the length is correct
void RegisterUsername()
{
    bool registered = false;
    while (registered != true)
    {
        string sRegisterUsername
        cout << "Please enter a username." << endl;
        cin >> sRegisterUsername;
        if ( sRegisterUsername.size() >= 20 )
        {
            cout << "Username can't be more than 20 characters long." << endl;
        }
        else if ( sRegisterUsername.size() <=5  ) 
        {
            cout << "Username can't be less than 5 characters long." << endl;
        }
        else 
        {
            cout << "Username: " << sRegisterUsername << " successful." << endl;
            registered = true;
        }
    }
}

void RegisterPassword()
{
    // Similar code goes here.
}

void CallCommandRegister()
{
    RegisterUsername();
    RegisterPassword();
}

Of course, from here you could do all sorts of fancy things, like keeping track of how many tries the user makes to register and then exiting. You could even return the value of the username and password and display them at the end of CallCommandRegister(), but I'll let you figure that one out. :)

Hope this helps.

[Disch]

EDIT:

I should really read other replies..... yulingo just said the exact same thing as me.