title: Category is implementing a method which also be implemented in primary class : `viewWillAppear:`
body: <p>I'm trying to category UIViewController to override <code>viewWillAppear:</code>. But getting this warning.</p>
  
  <blockquote>
    <p>Category is implementing a method which also be implemented in primary
    class</p>
  </blockquote>
  
  <pre><code>@implementation UIViewController (ViewWillAppearCategory)
  
  -(void)viewWillAppear:(BOOL)animated
  {
      //.........
  }
  
  @end
  </code></pre>
  
  <p>I want to do some stuff during view appear in all screen, So <strong>I don't want to touch in all screen</strong>. that's why, go with category.</p>
  
  <p>I may implement some method in sub class and I can call that method in all VC(all Screen). But I don't want this. It automatically invoke in view will appear call. Is this any idea to do this or did any mistake in above?</p>
  
  <p><strong>Note:</strong> This code will <strong>only appear in development phase</strong> for some testing purpose. So I'll remove this code when go with app store. So It should be easier task during removal, that is I won't touch all screen. I won't keep this code during submission to app store.</p>