title: Compiler warning about "Semantic Issue" -- how to fix?
body: <p>I receive this warning when building my app:    </p>
  
  <blockquote>
    <p>warning: Semantic Issue: Local declaration of 'datePicker' hides instance variable</p>
  </blockquote>
  
  <p>What does this mean and how do I fix it?</p>