title: how do i solve apple mach-o linker error? Xcode 6.4
body: <p>Every time i insert these two lines of code i get this error message and i dont understand why at all.</p>
  
  <pre><code>   NSTimer *BirdMovement;
  NSTimer *TunnelMovement;
  </code></pre>
  
  <p>Here is the whole Script</p>
  
  <pre><code>#import &lt;UIKit/UIKit.h&gt;
  
  int BirdFlight;
  int RandomTopTunnelPosition;
  int RandomBottomTunnelPosition;
  int ScoreNumber;
  NSInteger HighScoreNumber;
  
  @interface Game : UIViewController
  {
  
      IBOutlet UIImageView *Bird;
      IBOutlet UIButton *StartGame;
      IBOutlet UIImageView *TunnelUp;
      IBOutlet UIImageView *TunnelDown;
      IBOutlet UIImageView *Top;
      IBOutlet UIImageView *Bottom;
      IBOutlet UIButton *Exit;
      IBOutlet UILabel *ScoreLabel;
  
  
      NSTimer *BirdMovement;
      NSTimer *TunnelMovement;
  
  }
  
  -(IBAction)StartGame:(id)sender;
  -(void)BirdMoving;
  -(void)TunnelMoving;
  -(void)PlaceTunnels;
  -(void)Score;
  -(void)GameOver;
  
  @end
  </code></pre>
  
  <p>I dont think the other Scripts are the issue, if anyone has an idea id be thankful. </p>