Why does isEqualToString not work for NSString? - objective-c

Question

I am trying to code the login process for an iPhone app in XCode. The problem is with the NSString serverOutput below. When I print it using printf(serverOutput.UTF8String); it prints 'Yes' to the console. However when I compare serverOutput to "Yes" it doesn't work. Any help would be appreciated. Here's my code:
- (IBAction) loginButton: (id) sender
{
// TODO: spawn a login thread
indicator.hidden = FALSE;
[indicator startAnimating];
NSString *post =[NSString stringWithFormat:#"username=%#&password=%#",userName.text, password.text];
NSString *hostStr = #"http://10.243.1.184/connectDB.php?";
hostStr = [hostStr stringByAppendingString:post];
NSData *dataURL = [NSData dataWithContentsOfURL: [ NSURL URLWithString: hostStr ]];
NSString *serverOutput = [[NSString alloc] initWithData:dataURL encoding: NSASCIIStringEncoding];
printf(serverOutput.UTF8String);
if([serverOutput isEqualToString:#"Yes"]){
UIAlertView *alertsuccess = [[UIAlertView alloc] initWithTitle:#"Congrats" message:#"You are authorized"
delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil, nil];
[alertsuccess show];
[alertsuccess release];
}
else {
UIAlertView *alertsuccess = [[UIAlertView alloc] initWithTitle:#"Error" message:#"Username or Password Incorrect"
delegate:self cancelButtonTitle:#"OK"otherButtonTitles:nil, nil];
[alertsuccess show];
[alertsuccess release];
//[self.navigationController pushViewController:DashboardViewController animated:YES];
loginbutton.enabled = TRUE;
}
loginbutton.enabled = FALSE;
}

Answer 1

Based on helping others with similar situations I would say the problem is that the response from the server isn't just the string "Yes". Most likely there is some whitespace before and/or after the text. Perhaps a stray newline or two.
Try this:
NSString *serverOutput = [[NSString alloc] initWithData:dataURL encoding: NSASCIIStringEncoding];
NSLog(#"Result = '%#'", serverOutput); // look for space between quotes
serverOutput = [serverOutput stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];