andresbrun

class BallView: UIImageView {
    init(size: CGFloat) {
        super.init(frame: CGRect(origin: .zero, size: CGSize(width: size, height: size)))
        image = UIImage(named: "basketball-png-0")
        contentMode = .scaleToFill
        layer.cornerRadius = size * 0.5
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")

andresbrun

let pushBehaviour = UIPushBehavior(items: [mainModalView], mode: .instantaneous)
pushBehaviour.pushDirection = velocity.vector * Constants.pushForceRatio
pushBehaviour.setTargetOffsetFromCenter(offset, for: mainModalView)
animator.addBehavior(pushBehaviour)

animator.addBehavior(gravityBehaviour)

animator.removeBehaviors(itemsAttachmentBehaviours)

// Handy extension

andresbrun

modalViewExitBehaviour = UIDynamicItemBehavior(items: [targetView])
// Action is called in every animation step
modalViewExitBehaviour.action = { [unowned self] _ in
    // Check if all views are outside of the reference frame
    if !self.allViews.contains(where: { $0.frame.intersects(self.superview.bounds) }) {
        self.onDismiss?()
    }
}
animator?.addBehavior(modalViewExitBehaviour)