這30天已經是在寫日記了寫給自己看的....哈哈

DynamicBehavior
可以建立一個 dynamicbehavior的class把你要的behavior都放進去

import UIKit

class FallingObjBehavior: UIDynamicBehavior {
//你的behavior
    private let gravity = UIGravityBehavior()
    private let collider:UICollisionBehavior = {
        let collider = UICollisionBehavior()
        collider.translatesReferenceBoundsIntoBoundary = true
        return collider
    }()
    private let itemBehavior : UIDynamicItemBehavior = {
        let dib = UIDynamicItemBehavior()
        dib.allowsRotation = true
        dib.elasticity = 0.75
        return dib
    }()
    
    //把behavior加入
    override init() {
        super.init()
        addChildBehavior(gravity)
        addChildBehavior(collider)
        addChildBehavior(itemBehavior)
    }
    
    func addBarrier(path : UIBezierPath , named name : String) {
        collider.removeBoundary(withIdentifier: name as NSCopying)
        collider.addBoundary(withIdentifier: name as NSCopying, for: path)
    }
    將物件套用Behavior
    func addItem(item : UIDynamicItem) {
        gravity.addItem(item)
        collider.addItem(item)
        itemBehavior.addItem(item)
    }
    
    func removeItem(item : UIDynamicItem) {
        gravity.removeItem(item)
        collider.removeItem(item)
        itemBehavior.removeItem(item)
    }
}

Demo裡畫出View的方法
建立一個Class專門畫View
你的View繼承這個class
只要bPath有東西塞進去
就會畫出來

import UIKit

class NamedBezierPathView: UIView {
    var bPath = [String:UIBezierPath](){
        didSet{
            setNeedsDisplay()
        }
    }
    
    // Only override draw() if you perform custom drawing.
    // An empty implementation adversely affects performance during animation.
    override func draw(_ rect: CGRect) {
        // Drawing code
        for (_, path) in bPath {
            path.stroke()
        }
    }
    
}

各個Random的func
紀錄一下

extension CGFloat {
    static func random(max: Int) -> CGFloat {
        return CGFloat(arc4random() % UInt32(max))
    }
}

extension UIColor {
    class var random: UIColor {
        switch arc4random()%5 {
        case 0: return UIColor.green
        case 1: return UIColor.blue
        case 2: return UIColor.orange
        case 3: return UIColor.red
        case 4: return UIColor.purple
        default: return UIColor.black
        }
    }
}

extension CGRect {
    var mid: CGPoint { return CGPoint(x: midX, y: midY) }
    var upperLeft: CGPoint { return CGPoint(x: minX, y: minY) }
    var lowerLeft: CGPoint { return CGPoint(x: minX, y: maxY) }
    var upperRight: CGPoint { return CGPoint(x: maxX, y: minY) }
    var lowerRight: CGPoint { return CGPoint(x: maxX, y: maxY) }
    
    init(center: CGPoint, size: CGSize) {
        let upperLeft = CGPoint(x: center.x-size.width/2, y: center.y-size.height/2)
        self.init(origin: upperLeft, size: size)
    }
}

extension UIView {
    func hitTest(p: CGPoint) -> UIView? {
        return hitTest(p, with: nil)
    }
}

extension UIBezierPath {
    class func lineFrom(from: CGPoint, to: CGPoint) -> UIBezierPath {
        let path = UIBezierPath()
        path.move(to: from)
        path.addLine(to: to)
        return path
    }
}

最近好像有點消化不良