Extension to create Timer/CADisplayLink which don't strongly reference their target

weak-target-for-timer.swift

private class WeakTarget: NSObject {
	private(set) weak var target: AnyObject?
	let selector: Selector

	static let triggerSelector = #selector(WeakTarget.timerDidTrigger(parameter:))

	init(_ target: AnyObject, selector: Selector) {
		self.target = target
		self.selector = selector
	}

	@objc private func timerDidTrigger(parameter: Any) {
		_ = self.target?.perform(self.selector, with: parameter)
	}
}

extension Timer {
	convenience init(timeInterval ti: TimeInterval, weakTarget: AnyObject, selector: Selector, userInfo: Any?, repeats: Bool) {
		self.init(timeInterval: ti, target: WeakTarget(weakTarget, selector: selector), selector: WeakTarget.triggerSelector, userInfo: userInfo, repeats: repeats)
	}

	class func scheduledTimer(timeInterval ti: TimeInterval, weakTarget: AnyObject, selector: Selector, userInfo: Any?, repeats: Bool) -> Timer {
		return self.scheduledTimer(timeInterval: ti, target: WeakTarget(weakTarget, selector: selector), selector: WeakTarget.triggerSelector, userInfo: userInfo, repeats: repeats)
	}
}

extension CADisplayLink {
	convenience init(weakTarget: AnyObject, selector: Selector) {
		self.init(target: WeakTarget(weakTarget, selector: selector), selector: WeakTarget.triggerSelector)
	}
}