アニメーションするグラフ

AnimatableGraph.swift

import UIKit

class AnimatableGraph : CALayer {
    
    var degree: Double = 0.0 {
        didSet{
            if(degree < 0){
                self.degree = 0
            }else if(degree > 360){
                self.degree = 360.0
            }
        }
    }
    
    override init!() {
        super.init()
        self.needsDisplayOnBoundsChange = true
        self.contentsScale = UIScreen.mainScreen().scale
    }
    
    // アニメーション時にはこのイニシャライザを実装する必要がある
    override init!(layer: AnyObject!) {
        if let layer = layer as? AnimatableGraph {
            degree = layer.degree
        }
        super.init(layer: layer)
        needsDisplayOnBoundsChange = true
        contentsScale = UIScreen.mainScreen().scale
    }

    // requiredなので
    required init(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    
    override class func needsDisplayForKey(key: String!) -> Bool {
        if(key == "degree"){
            return true
        }
        
        return super.needsDisplayForKey(key)
    }

    
    override func drawInContext(ctx: CGContext!) {
        
        CGContextSaveGState(ctx)

        var x = self.bounds.origin.x
        x += self.bounds.size.width/2
        
        var y = self.bounds.origin.y
        y += self.bounds.size.height/2

        CGContextSetLineWidth(ctx, 0)
        
        var path = CGPathCreateMutable()
        CGPathAddArc(path, nil, x, y, CGFloat(x-10), 0, CGFloat(M_PI * 2), false)
        CGContextAddPath(ctx, path);
        CGContextSetRGBFillColor(ctx, CGFloat(0.6), CGFloat(0.6), CGFloat(0.6), CGFloat(1.0));
        CGContextDrawPath(ctx, kCGPathFillStroke);
        
        // 3時の方向が0度なので補正
        var aDegree = degree - 180.0;
        
        var graph = CGPathCreateMutable()
        CGPathAddArc(graph, nil, x, y, CGFloat(x-10), CGFloat((M_PI * -1.0)), CGFloat((M_PI * 2.0) * (aDegree / 360.0)), false)
        CGPathAddLineToPoint(graph, nil, x, y)
        CGContextAddPath(ctx, graph);
        CGContextSetRGBFillColor(ctx, CGFloat(232.0/255.0), CGFloat(38.0/255.0), CGFloat(107.0/255.0), CGFloat(1.0))
        CGContextDrawPath(ctx, kCGPathFillStroke);
        
        CGContextRestoreGState(ctx);
    }
}

ViewController.swift

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        
        var graph = AnimatableGraph()
        graph.frame = CGRect(x: 50, y: 50, width: 200, height: 200)
        self.view.layer.addSublayer(graph)
        
        var animation = CABasicAnimation(keyPath: "degree")
        animation.duration = 10
        animation.repeatCount = 1
        animation.fromValue = 0.0
        animation.toValue = 360.0
        animation.removedOnCompletion = false
        animation.fillMode = kCAFillModeForwards
        graph.addAnimation(animation, forKey: "key")
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}