Loading spinner to drop into your iOS projects (Swift)

Loading.swift

// Display your spinner by calling Loading.start() and hide it with Loading.stop()
// Include asset 'spinner.png'
import UIKit

class Loading {
	static let backgroundColor = UIColor(red: 46.0/255.0, green: 204.0/255.0, blue: 113.0/255.0, alpha: 0.44)
	static let fade = 0.1

	static var indicator: UIView = {
		var view = UIView()
		let screen: CGRect = UIScreen.mainScreen().bounds
		var side = screen.width / 4
		var x = (screen.width / 2) - (side / 2)
		var y = (screen.height / 2) - (side / 2)
		view.frame = CGRect(x: x, y: y, width: side, height: side)
		view.backgroundColor = backgroundColor
		view.layer.cornerRadius = 10
		view.alpha = 0.0
		view.tag = 1
		let image = UIImage(named: "spinner.png")
		let imageView = UIImageView(image: image!)
		imageView.frame = CGRect(x: side / 4, y: side / 4, width: side / 2, height: side / 2)
		view.addSubview(imageView)
		return view
	}()

	static var animation: CABasicAnimation = {
		let rotateAnimation = CABasicAnimation(keyPath: "transform.rotation")
		rotateAnimation.fromValue = 0.0
		rotateAnimation.toValue = CGFloat(M_PI * 2.0)
		rotateAnimation.duration = 2.0
		rotateAnimation.repeatCount = Float.infinity
		return rotateAnimation
	}()

	static func start () {
		if let window :UIWindow = UIApplication.sharedApplication().keyWindow {
			var found: Bool = false
			for subview in window.subviews {
				if subview.tag == 1 {
					found = true
				}
			}
			if !found {
				for subview in indicator.subviews {
					subview.layer.addAnimation(animation, forKey: nil)
				}
				window.addSubview(indicator)
				UIView.animateWithDuration(fade, animations: {
					self.indicator.alpha = 1.0
				})
			}
		}
	}

	static func stop () {
		UIView.animateWithDuration(fade, animations: {
			self.indicator.alpha = 0.0
		}, completion: { (value: Bool) in
			self.indicator.removeFromSuperview()
			for subview in self.indicator.subviews {
				subview.layer.removeAllAnimations()
			}
		})
	}
}