title: Assigning NSMutableString To UILabel Text
body: <p>I am making a fraction calculator app from the Programming In Objective-C 2.0 book. I am using XCode 4.1 for Lion. I have completely and successfully without any error typed in the code. But when I press a number button while the app is running, the label doesn't input any text. When I press a number button, it should find the UIButton senders tag (which I have allocated)</p>
  
  <pre><code>   -(IBAction)clickDigit:(UIButton *)sender {
  
  int digit = sender.tag;
  
  [self processDigit:digit];
      }
  </code></pre>
  
  <p>and it gets sent to this code:</p>
  
  <pre><code>  -(void)processDigit:(int)digit {
  
  currentNumber = currentNumber * 10 + digit;
  
  [displayString appendString:[NSString stringWithFormat:@"%i", digit]];
  display.text = displayString;
  
  NSLog(@"Processed");
  
      }
  </code></pre>
  
  <p>The console DOES print Processed. Indicating that this button is working, so the problem lies in this line of code:</p>
  
  <pre><code>[displayString appendString:[NSString stringWithFormat:@"%i", digit]];
  display.text = displayString;
  </code></pre>
  
  <p>display is a UILabel, it is an instance variable but it is not an IBOutlet but is declared as an IBOutlet in its property. </p>
  
  <pre><code>@property (nonatomic, retain)IBOutlet UILabel *display;
  </code></pre>
  
  <p>I have connected the label on the .xib screen using the connection to code assistant thing. I can literally connect it to the declarations. So I connected it to the property.</p>
  
  <p>Now, the problem lies in the fact that display is a UILabel and its text property requires an NSString not a NSMutableString right? But an NSString cannot append a string and many other methods that I need it to do for this app. How can I make this work?</p>