SKPhysicsContact is there any way to determine which body is A and B?
问题 in SpriteKit we detect the in the didBeginContact method. but this looks a bit stupid to do something like that: func didBeginContact(contact: SKPhysicsContact) { if let contactA = contact.bodyA.node?.name { if let contactB = contact.bodyB.node?.name { //now that we have safely unwrapped these nodes, we can operate on them if contactA == "ball" { collisionBetweenBall(contact.bodyA.node!, object: contact.bodyB.node!) } else if contactB == "ball" { collisionBetweenBall(contact.bodyB.node!,