SKPhysicsContact
A description of the contact between two physics bodies.
Declaration
class SKPhysicsContactOverview
An SKPhysicsContact object is created automatically by SpriteKit to describe a contact between two physical bodies in a physics world.To receive contact messages, read the physicsWorld property of an SKScene object you are interested in, and assign its contactDelegate property to point to an object that implements the SKPhysicsContactDelegate protocol. Then, for each physics body in your scene, set the categoryBitMask and contactTestBitMask properties to define which interactions should generate contact messages.