用Swift实现笑脸

写在前面：这是根据Stanford的Swift课程敲的一个小程序；

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Swift 及 storyboard知识点：
1、UIViewController 及 UIView的布局
2、CGFloat CGPoint、UIColor的使用
3、UIBezierPath的使用

实现效果：

1、一个简单线条组成的笑脸（可变成不高兴脸）
2、旋转屏幕实现redraw效果

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实现旋转的redraw

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笑脸实现相关代码：

////  FaceView.swift//  Happiness////  Created by VincentYau on 5/5/16.//  Copyright (c) 2016 VincentYau. All rights reserved.//import UIKitclass FaceView: UIView{    var lineWidth: CGFloat = 3{        didSet {setNeedsDisplay()}    }    var color: UIColor = UIColor.redColor(){didSet {setNeedsDisplay()}}    var scale: CGFloat = 0.90 {didSet {setNeedsDisplay()}}    var faceCenter: CGPoint {        return convertPoint(center, fromView: superview)    }    var faceRadius: CGFloat {        return min(bounds.size.width, bounds.size.height) / 2 * scale    }    private struct Scaling {        static let FaceRadiusToEyeRadiusRatio: CGFloat = 10        static let FaceRadiusToEyeOffsetRatio: CGFloat = 3        static let FaceRadiusToEyeSeparationRatio: CGFloat = 1.5        static let FaceRadiusToMouthWidthRatio: CGFloat = 1        static let FaceRadiusToMouthHeightRatio: CGFloat = 3        static let FaceRadiusToMouthOffsetRatio: CGFloat = 3    }    private enum Eye { case Left, Right }    private func bezierPathForEye(whichEye: Eye) -> UIBezierPath    {        let eyeRadius = faceRadius / Scaling.FaceRadiusToEyeRadiusRatio        let eyeVerticalOffset = faceRadius / Scaling.FaceRadiusToEyeOffsetRatio        let eyeHorizontalSeparation = faceRadius / Scaling.FaceRadiusToEyeSeparationRatio        var eyeCenter = faceCenter        eyeCenter.y -= eyeVerticalOffset        switch whichEye        {        case .Left: eyeCenter.x -= eyeHorizontalSeparation / 2        case .Right: eyeCenter.x += eyeHorizontalSeparation / 2        }        let path = UIBezierPath(arcCenter: eyeCenter, radius: eyeRadius, startAngle: 0, endAngle: CGFloat(2*M_PI), clockwise: true)        path.lineWidth = lineWidth        return path    }    private func bezierPathForSmile(fractionOfMaxSmile: Double ) -> UIBezierPath    {        let mouthWidth = faceRadius / Scaling.FaceRadiusToMouthWidthRatio        let mouthHeight = faceRadius / Scaling.FaceRadiusToMouthHeightRatio        let mouthVerticalOffset = faceRadius / Scaling.FaceRadiusToMouthOffsetRatio        let smileHeight = CGFloat(max(min(fractionOfMaxSmile, 1), -1)) * mouthHeight        let start = CGPoint(x: faceCenter.x - mouthWidth / 2, y: faceCenter.y + mouthVerticalOffset)        let end = CGPoint(x: start.x + mouthWidth, y: start.y)        let cp1 = CGPoint(x: start.x + mouthWidth / 3,y: start.y + smileHeight)        let cp2 = CGPoint(x: end.x - mouthWidth / 3, y: cp1.y)        let path = UIBezierPath()        path.moveToPoint(start)        path.addCurveToPoint(end, controlPoint1: cp1, controlPoint2: cp2)        return path    }    override func drawRect(rect: CGRect)    {        let facePath = UIBezierPath(arcCenter: faceCenter, radius: faceRadius, startAngle: 0, endAngle: CGFloat(2*M_PI), clockwise: true)        facePath.lineWidth = lineWidth        color.set()        facePath.stroke()        bezierPathForEye(.Left).stroke()        bezierPathForEye(.Right).stroke()        let smiliness = -0.5        let smilePath = bezierPathForSmile(smiliness)        smilePath.stroke()    }}

PS：以后写代码要记住写注释；