Shows the different ways to define a attachmentBehaviour

UIAttachmentBehaviour.swift

// Dragging an element with a PanGestureRecognizer for instance
let dragAttachmentBehaviour = UIAttachmentBehavior(item: targetView,
                                                   offsetFromCenter: offsetFromCenter,
                                                   attachedToAnchor: dragLocation)

// Attaching two box in a chain
let boxAttachmentBehaviour = UIAttachmentBehavior(item: box1, 
                                                  offsetFromCenter: UIOffset(horizontal: 0, vertical: box1.bounds.midY), 
                                                  attachedTo: box2, 
                                                  offsetFromCenter: UIOffset(horizontal: 0, vertical: -box2.bounds.midY))

// NOTE: all offsetFromCenter are optional. They are the center of the view by default