Create a swift version of this amazing category

This is a line-by-line translation of the original objective-c code to swift.

UIView+Glow.swift

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+//
+//  UIView+Glow.swift
+//
+//  Translated by James Perlman on 9/7/16.
+//
+
+import UIKit
+import ObjectiveC
+import Dispatch
+
+private var GLOWVIEW_KEY = "GLOWVIEW"
+
+extension UIView {
+    var glowView: UIView? {
+        get {
+            return objc_getAssociatedObject(self, &GLOWVIEW_KEY) as? UIView
+        }
+        set(newGlowView) {
+            objc_setAssociatedObject(self, &GLOWVIEW_KEY, newGlowView!, .OBJC_ASSOCIATION_RETAIN)
+        }
+    }
+
+    func startGlowingWithColor(color:UIColor, intensity:CGFloat) {
+        self.startGlowingWithColor(color, fromIntensity: 0.1, toIntensity: intensity, repeat: true)
+    }
+
+    func startGlowingWithColor(color:UIColor, fromIntensity:CGFloat, toIntensity:CGFloat, repeat shouldRepeat:Bool) {
+        // If we're already glowing, don't bother
+        if self.glowView != nil {
+            return
+        }
+
+        // The glow image is taken from the current view's appearance.
+        // As a side effect, if the view's content, size or shape changes,
+        // the glow won't update.
+        var image:UIImage
+
+        UIGraphicsBeginImageContextWithOptions(self.bounds.size, false, UIScreen.mainScreen().scale); do {
+            self.layer.renderInContext(UIGraphicsGetCurrentContext()!)
+
+            let path = UIBezierPath(rect: CGRectMake(0, 0, self.bounds.size.width, self.bounds.size.height));
+
+            color.setFill();
+
+            path.fillWithBlendMode(.SourceAtop, alpha:1.0);
+
+
+            image = UIGraphicsGetImageFromCurrentImageContext();
+        }
+
+        UIGraphicsEndImageContext()
+
+        // Make the glowing view itself, and position it at the same
+        // point as ourself. Overlay it over ourself.
+        let glowView = UIImageView(image: image)
+        glowView.center = self.center
+        self.superview!.insertSubview(glowView, aboveSubview:self)
+
+        // We don't want to show the image, but rather a shadow created by
+        // Core Animation. By setting the shadow to white and the shadow radius to
+        // something large, we get a pleasing glow.
+        glowView.alpha = 0
+        glowView.layer.shadowColor = color.CGColor
+        glowView.layer.shadowOffset = CGSizeZero
+        glowView.layer.shadowRadius = 10
+        glowView.layer.shadowOpacity = 1.0
+
+        // Create an animation that slowly fades the glow view in and out forever.
+        let animation = CABasicAnimation(keyPath: "opacity")
+        animation.fromValue = fromIntensity
+        animation.toValue = toIntensity
+        animation.repeatCount = shouldRepeat ? .infinity : 0 // HUGE_VAL = .infinity / Thanks http://stackoverflow.com/questions/7082578/cabasicanimation-unlimited-repeat-without-huge-valf
+        animation.duration = 1.0
+        animation.autoreverses = true
+        animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
+
+        glowView.layer.addAnimation(animation, forKey: "pulse")
+
+        // Finally, keep a reference to this around so it can be removed later
+        self.glowView = glowView
+    }
+
+    func glowOnceAtLocation(point: CGPoint, inView view:UIView) {
+        self.startGlowingWithColor(UIColor.whiteColor(), fromIntensity: 0, toIntensity: 0.6, repeat: false)
+
+        self.glowView!.center = point
+        view.addSubview(self.glowView!)
+
+        let delayInSeconds:Int64 = 2
+        let popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * Int64(NSEC_PER_SEC))
+        dispatch_after(popTime, dispatch_get_main_queue()) { [weak self] in
+            self?.stopGlowing()
+        }
+    }
+
+    func glowOnce() {
+        self.startGlowing()
+
+        let delayInSeconds:Int64 = 2;
+        let popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * Int64(NSEC_PER_SEC))
+        dispatch_after(popTime, dispatch_get_main_queue()){
+            self.stopGlowing()
+        }
+
+    }
+
+    // Create a pulsing, glowing view based on this one.
+    func startGlowing() {
+        self.startGlowingWithColor(UIColor.whiteColor(), intensity:0.6);
+    }
+
+    // Stop glowing by removing the glowing view from the superview
+    // and removing the association between it and this object.
+    func stopGlowing() {
+        self.glowView!.removeFromSuperview()
+        self.glowView = nil
+    }
+
+}