title: UIView get width/height without UIViewController
body: <p>I have this:</p>
  
  <pre><code>class SheetView: UIView {
  
    override init(frame: CGRect) {
      super.init(frame: frame)
  
      RCTLogInfo("SHEET VIEW INIT'ED")
      let width = String(format:"%.3f", Double(self.frame.size.width));
      let height = String(format:"%.3f", Double(self.frame.size.height));
      RCTLogInfo("Width: " + width + ", Height: " + height);
  
    }
  
    required init?(coder aDecoder: NSCoder) {
      fatalError("init(coder:) has not been implemented")
    }
  
  }
  </code></pre>
  
  <p>However width and height are always 0. Reading here <a href="https://stackoverflow.com/q/26578234/1828637">Access UIView width at runtime</a> it seems I need a <code>viewDidLayoutSubviews</code> but a <code>UIView</code> doesn't seem to have this. I have to use <code>UIViewController</code> to use <code>viewDidLayoutSubviews</code>, however I cannot change from <code>UIView</code>, because the place this component gets used, expects a <code>UIView</code>:</p>
  
  <pre><code>class SheetViewManager : RCTViewManager {
  
    override func view() -&gt; UIView! {
      return SheetView();
    }
  
  }
  </code></pre>
  
  <p>Is there anyway to get height/width in just the <code>UIView</code>?</p>