title: Simple math app terminated in Xcode- Why?
body: <p>Alright, so I'm trying to do something very, very simple: Multiplying the user input from one textfield by another textfield and feeding out the answer through a label. There are no error messages, but when I try to run the app, the simulator screen goes black and Xcode says this: </p>
  
  <p>Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[ setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key outputlabel.'</p>
  
  <p>I have no idea why it is doing this. Any suggestions? Please be extremely specific as I am new to programming. </p>
  
  <p>My code: </p>
  
  <pre><code>//
  //  ViewController.h
  //  Cramer
  
  #import &lt;UIKit/UIKit.h&gt;
  
  @interface ViewController : UIViewController
  
  // Objects are given addresses:
  
  
  @property (weak, nonatomic) IBOutlet UITextField *box_a;
  @property (weak, nonatomic) IBOutlet UITextField *box_b;
  @property (weak, nonatomic) IBOutlet UILabel *hiLabel;
  
  @property (weak, nonatomic) IBOutlet UIButton *clickButton;
  
  @end
  </code></pre>
  
  <p>AND</p>
  
  <pre><code>//
  //  ViewController.m
  //  Cramer
  
  
  #import "ViewController.h"
  
  @interface ViewController ()
  
  @end
  
  @implementation ViewController
  
  - (void)viewDidLoad
  {
      [super viewDidLoad];
      // Do any additional setup after loading the view, typically from a nib.
  }
  
  - (void)didReceiveMemoryWarning
  {
      [super didReceiveMemoryWarning];
      // Dispose of any resources that can be recreated.
  }
  
  // Math takes place:
  
  - (IBAction)clickButton:(id)sender {
  
      NSInteger number1 = [self.box_a.text integerValue];
      NSInteger number2 = [self.box_b.text integerValue];
  
      NSInteger prod = number1 * number2;
  
      self.hiLabel.text =  [NSString stringWithFormat:@"%@", @(prod)];
  
  }
  
  @end
  </code></pre>