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private func strokeCircle() {
    let context = UIGraphicsGetCurrentContext()
    let lineWidth: CGFloat = 5
    let innerRect: CGRect = CGRectInset(self.bounds, lineWidth/2, lineWidth/2)
    let strokeColor: CGColor = UIColor.blueColor().CGColor
    
    CGContextSetStrokeColorWithColor(context, strokeColor)
    CGContextSetLineWidth(context, lineWidth)
    CGContextStrokeEllipseInRect(context, innerRect)
  }

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import AVFoundation

private func showDialogWithTitle(title: String?, msg: String?) {
    let alertController = UIAlertController(title: title, message: msg, preferredStyle: UIAlertControllerStyle.Alert)
    alertController.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil))
    self.presentViewController(alertController, animated: true, completion: nil)
  }

  @IBAction func didTapButton(sender: AnyObject) {
    let authorizationStatus: AVAuthorizationStatus = AVCaptureDevice.authorizationStatusForMediaType(AVMediaTypeVideo)

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  var block: dispatch_block_t?
  
  override func viewDidLoad() {
    super.viewDidLoad()    
  }
  
  override func viewDidAppear(animated: Bool) {
    block = dispatch_block_create(DISPATCH_BLOCK_INHERIT_QOS_CLASS) {
      print("I executed")
    }

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// iOS 9 or Above
// Reference: https://www.raywenderlich.com/125718/coding-auto-layout
//
avatarView.translatesAutoresizingMaskIntoConstraints = false
avatarView.topAnchor.constraintEqualToAnchor(topLayoutGuide.bottomAnchor).active = true
avatarView.leadingAnchor.constraintEqualToAnchor(view.layoutMarginsGuide.leadingAnchor).active = true
chapterLabel.centerXAnchor.constraintEqualToAnchor(view.centerXAnchor).active = true
avatarView.bottomAnchor.constraintEqualToAnchor(chapterLabel.topAnchor,constant: -10).active = true
chapterLabel.setContentHuggingPriority(UILayoutPriorityRequired, forAxis: .Vertical)
chapterLabel.setContentCompressionResistancePriority(UILayoutPriorityRequired, forAxis: .Vertical)

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//
// Reference: https://www.raywenderlich.com/79150/grand-central-dispatch-tutorial-swift-part-2
//

var GlobalMainQueue: dispatch_queue_t {
  return dispatch_get_main_queue()
}
 
var GlobalUserInteractiveQueue: dispatch_queue_t {
  return dispatch_get_global_queue(Int(QOS_CLASS_USER_INTERACTIVE.value), 0)

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//
// Reference from http://samwize.com/2015/11/06/guide-to-customizing-uitableview-section-header-footer/
//
class TableSectionHeader: UITableViewHeaderFooterView {
    @IBOutlet weak var titleLabel: UILabel!
}

let nib = UINib(nibName: "TableSectionHeader", bundle: nil)
tableView.registerNib(nib, forHeaderFooterViewReuseIdentifier: "TableSectionHeader")

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func tableView(tableView: UITableView, willDisplayCell cell: UITableViewCell, forRowAtIndexPath indexPath: NSIndexPath) {
    cell.separatorInset = UIEdgeInsetsZero
    cell.preservesSuperviewLayoutMargins = false
    cell.layoutMargins = UIEdgeInsetsMake(0, 8, 0, 0)
  }

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class MyView: UIView {

  @IBOutlet weak var label: UILabel!
 
  class func instanceFromNib() -> MyView {
    return UINib(nibName: "MyView", bundle: nil).instantiateWithOwner(nil, options: nil)[0] as! MyView
  }

}

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func getSearchTextField() -> UITextField {
    return valueForKey("_searchField") as! UITextField
  }

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extension UIViewController {
  class func currentViewController() -> UIViewController {
    let rootViewController = UIApplication.sharedApplication().delegate?.window!?.rootViewController
    
    func findBestViewController(vc: UIViewController) -> UIViewController? {
      if let pvc = vc.presentedViewController {
        return findBestViewController(pvc)
      }
      else if let svc = vc as? UISplitViewController where svc.viewControllers.count > 0 {
        return findBestViewController(svc.viewControllers.last!)