CALayer extension for using blocks instead of animation delegates

ClosureBasedCAAnimationDelegate.swift

//
//  CALayerExtensions.swift
//

import QuartzCore

internal typealias LayerAnimationBeginClosure = (CAAnimation) -> Void
internal typealias LayerAnimationCompletionClosure = (CAAnimation, Bool) -> Void

// MARK: LayerAnimationDelegate Class -
private class LayerAnimationDelegate: NSObject, CAAnimationDelegate {
    
    var beginClosure: LayerAnimationBeginClosure?
    var completionClosure: LayerAnimationCompletionClosure?
    
    // MARK: - Protocol Implementations
    
    // MARK: CAAnimation (Informal)
    
    func animationDidStart(_ anim: CAAnimation) {
        guard let beginClosure = beginClosure else { return }
        beginClosure(anim)
    }
    
    func animationDidStop(_ anim: CAAnimation, finished flag: Bool) {
        guard let completionClosure = completionClosure else { return }
        completionClosure(anim, flag)
    }
    
}

// MARK: - CALayer Extension -
extension CALayer {
    
    // MARK: - Conveniences for Adding Animations
    
    func add(animation: CAAnimation) {
        add(animation, forKey: nil)
    }
    
    func add(animation: CAAnimation,forKey key: String?, completionClosure: LayerAnimationCompletionClosure?) {
        add(animation: animation, forKey: key, beginClosure: nil, completionClosure: completionClosure)
    }
    
    func add(animation: CAAnimation, forKey key: String?, beginClosure: LayerAnimationBeginClosure?, completionClosure: LayerAnimationCompletionClosure?) {
        let animationDelegate = LayerAnimationDelegate()
        animationDelegate.beginClosure = beginClosure
        animationDelegate.completionClosure = completionClosure
        
        animation.delegate = animationDelegate
        
        add(animation, forKey: key)
    }
    
    func replace(animation: CAAnimation, forKey key: String) {
        replace(animation: animation, forKey: key, beginClosure: nil, completionClosure: nil)
    }
    
    func replace(animation: CAAnimation, forKey key: String, completionClosure: LayerAnimationCompletionClosure?) {
        replace(animation: animation, forKey: key, beginClosure: nil, completionClosure: completionClosure)
    }
    
    func replace(animation: CAAnimation, forKey key: String, beginClosure: LayerAnimationBeginClosure?, completionClosure: LayerAnimationCompletionClosure?) {
        removeAnimation(forKey: key)
        add(animation: animation, forKey: key, beginClosure: beginClosure, completionClosure: completionClosure)
    }
    
}