Simple pie chart drawing code for iOS using CAShapeLayer and UIBezierPath

piechart.swift

extension CGFloat {
    func radians() -> CGFloat {
        let b = CGFloat(M_PI) * (self/180)
        return b
    }
}

extension UIBezierPath {
    convenience init(circleSegmentCenter center:CGPoint, radius:CGFloat, startAngle:CGFloat, endAngle:CGFloat)
    {
        self.init()
        self.moveToPoint(CGPointMake(center.x, center.y))
        self.addArcWithCenter(center, radius:radius, startAngle:startAngle.radians(), endAngle: endAngle.radians(), clockwise:true)
        self.closePath()
    }
}



func pieChart(pieces:[(UIBezierPath, UIColor)], viewRect:CGRect) -> UIView {
    var layers = [CAShapeLayer]()
    for p in pieces {
        let layer = CAShapeLayer()
        layer.path = p.0.CGPath
        layer.fillColor = p.1.CGColor
        layer.strokeColor = UIColor.whiteColor().CGColor
        layers.append(layer)
    }
    let view = UIView(frame: viewRect)
    for l in layers {
        
        view.layer.addSublayer(l)
        
        
    }
    return view
}

let rectSize = CGRectMake(0,0,400,400)
let centrePointOfChart = CGPointMake(CGRectGetMidX(rectSize),CGRectGetMidY(rectSize))
let radius:CGFloat = 100
let piePieces = [(UIBezierPath(circleSegmentCenter: centrePointOfChart, radius: radius, startAngle: 250, endAngle: 360),UIColor.brownColor()), (UIBezierPath(circleSegmentCenter: centrePointOfChart, radius: radius, startAngle: 0, endAngle: 200),UIColor.orangeColor()), (UIBezierPath(circleSegmentCenter: centrePointOfChart, radius: radius, startAngle: 200, endAngle: 250),UIColor.lightGrayColor())]
pieChart(piePieces, viewRect: CGRectMake(0,0,400,400))

Hi,

Anyone knows how to convert these code to objective-c?