andresbrun

let animator = UIDynamicAnimator(referenceView: containerView)

let gravityBehaviour = UIGravityBehavior(items: [targetView])
gravityBehaviour.magnitude = 1.0 // gravity on earth
animator.addBehavior(gravityBehaviour)

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)