UIDynamicItem Gravity

GrowView.swift

import UIKit

class GrowView: UIView {
    
    var anim : UIDynamicAnimator!
    var grav : UIGravityBehavior!
    var coll : UICollisionBehavior!
    
    required init(coder aDecoder: NSCoder) {
        self.anim = nil
        self.grav = nil
        self.coll = nil

        super.init(coder: aDecoder)
    
    }
    
    override func awakeFromNib() {
        self.anim = UIDynamicAnimator(referenceView: self)

        let v = UIView(frame: CGRectMake(10,10,30,30))
        v.backgroundColor = UIColor.redColor()
        self.addSubview(v)
        
        self.grav = UIGravityBehavior(items: [v])
        self.coll = UICollisionBehavior(items: [v])
        
        self.anim.addBehavior(grav)
        self.anim.addBehavior(coll)
        
        coll.addBoundaryWithIdentifier("bottom", fromPoint: CGPointMake(0, self.frame.height), toPoint: CGPointMake(self.frame.width, self.frame.height))
        
        
    }
    
        override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
        let t =  touches.first
        let loc = t?.locationInView(self)
        
    
        let v = UIView(frame: CGRectMake(loc!.x,loc!.y,3,10))
        
        let c = [UIColor.redColor(), UIColor.greenColor(), UIColor.grayColor(), UIColor.whiteColor()
            , UIColor.purpleColor(), UIColor.yellowColor(), UIColor.magentaColor()]
        
        let index = Int(arc4random() % (UInt32(c.count)))
        
        v.backgroundColor = c[index]
        v.transform = CGAffineTransformMakeRotation(loc!.x / (loc!.y + 0.01))
        self.addSubview(v)
        
        
        self.grav.addItem(v)
        self.coll.addItem(v)
        
        
        
       
    }

    
    
    

}