title: this class is not key value coding-compliant for the key setOutput
body: <p>I am brand new to iOS/Objective-C and I am trying to learn. I am following along in Sam's Teach yourself iOS. I am doing a project called Hello Noun, where instead of displaying Hello World, it takes an input and displays "Hello Input". </p>
  
  <p>Working on the project, everything was fine, and there were no errors. But when I went to Build and then Run the app, it crashed saying; </p>
  
  <pre><code>'NSUnknownKeyException', reason: '[&lt;ViewController 0xa064620&gt; setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key setOutput.'
  </code></pre>
  
  <p>and pointed to main.m file highlighting these lines;</p>
  
  <pre><code>#import &lt;UIKit/UIKit.h&gt;
  
  #import "AppDelegate.h"
  
  int main(int argc, char * argv[])
  {
      @autoreleasepool {
          return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
      }
  }
  </code></pre>
  
  <p>The rest of the code used is below;</p>
  
  <p>ViewController.m</p>
  
  <pre><code>    @interface ViewController ()
  @property (weak, nonatomic) IBOutlet UILabel *userOutput;
  @property (weak, nonatomic) IBOutlet UITextField *userInput;
  - (IBAction)setOutput:(id)sender;
  @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.
  }
  
  - (IBAction)setOutput:(id)sender {
      self.userOutput.text=self.userInput.text;
  }
  @end
  </code></pre>
  
  <p>I am new to this, and I'm just getting my bearings so I'm not quite sure what is happening. Any help would be beyond appreciated. </p>