title: How do I call this methods with a parameter in ObjC
body: <p>I'm quiet new in ObjC and app programming. All I want to do is fade in an image. For that I did this:</p>
  
  <pre><code>-(IBAction)changeImg:(id)sender{
      myImgView.image = [UIImage imageNamed:@"image.png"];
      myImgView.alpha = 0;
      [UIView beginAnimations:nil context:nil];
      [UIView setAnimationDuration:1];
      myImgView.alpha = 1;
      [UIView commitAnimations];
  }
  </code></pre>
  
  <p>That works quiet good. But now I want to put the fade function into an own method and I don't know how to call that method:</p>
  
  <pre><code>-(IBAction)changeImg:(id)sender{
      myImgView.image = [UIImage imageNamed:@"image.png"];
      [myImgView fadeIn:self];
  }
  
  -(void) fadeIn:(UIImageView *) imgFade{
      imgFade.alpha = 0;
      [UIView beginAnimations:nil context:nil];
      [UIView setAnimationDuration:1];
      imgFade.alpha = 1;
      [UIView commitAnimations];
  }
  </code></pre>
  
  <p>When I call the method like this I get a warning:"<em>'UIImageView' may not respond to '-fadeIn:'</em>"</p>
  
  <p>Can anyone help me please?</p>
  
  <hr>
  
  <p>Sorry but I don't get it to work.
  The warning stays.
  And when I do it like kuroutadori suggested:</p>
  
  <pre><code>...
  self.alpha = 0;
  ...
  </code></pre>
  
  <p>I get an error:
  "<em>request for member 'alpha' in something not a structure or union</em>"</p>