Hit Testing and Collision Detection - Beginning Swift Games Development for iOS - page 216

In conjunction with this, you will also need to set the delegate to a class that will respond
to these collisions. In this case, you will set the mainScene 's contactDelegate to
self so that the GameViewController can react to the collisions.
mainScene.physicsWorld.contactDelegate = self
The SCNPhysicsContactDelegate has three protocols that you can use, as shown
in Listing 14-9 .
Listing 14-9 . SCNPhsicsContact Protocols
func physicsWorld(world: SCNPhysicsWorld, didBeginContact
contact: SCNPhysicsContact) {
println(“didBeginContact”)
}
func physicsWorld(world: SCNPhysicsWorld, didEndContact
contact: SCNPhysicsContact) {
println(“didEndContact”)
}
func physicsWorld(world: SCNPhysicsWorld, didUpdateContact
contact: SCNPhysicsContact) {
println("didUpdateContact")
}
You should add Listing 14-9 to your GameViewController . This time when you run
your game, you will get the notifications when your spaceman moves around and interacts
with the environment. For this game, however, you will be using only the didBe-
ginContact protocol. It will be at this time you check to see whether the contact object
has the node for the spaceman and the node for the enemy. To do this, you will keep
things simple and check nodeB for what type of contact was made in Listing 14-10 .
Listing 14-10 . SCNPhysicsWorld didBeginContact Protocol
func physicsWorld(world: SCNPhysicsWorld, didBeginContact
contact: SCNPhysicsContact) {
if contact.nodeB.physicsBody!.categoryBitMask ==
CollisionCategoryEnemy {
println("Enemy HIT!--------")