Collision detection between two sprites not working - ios

Question

I am trying to detect when the player object collides with the other objects in my game. This is my current code:
import SpriteKit
class GameScene: SKScene {
let player = SKSpriteNode(imageNamed: “Box”)
override func didMoveToView(view: SKView) {
backgroundColor = SKColor.whiteColor()
player.position = CGPoint(x: size.width/2, y: size.height/2)
addChild(player)
runAction(SKAction.repeatActionForever(
SKAction.sequence([
SKAction.runBlock(addObject),
SKAction.waitForDuration(1)
])
))
runAction(SKAction.repeatActionForever(
SKAction.sequence([
SKAction.runBlock(addSecondObject),
SKAction.waitForDuration(1)
])
))
}
override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {
for touch: AnyObject in touches {
let location = touch.locationInNode(self)
player.position = location
}
}
func EndGame() {
println("GAME OVER")
}
func Collision() {
if (CGRectIntersectsRect(player.frame, object.frame )) {
[EndGame];
}
if (CGRectIntersectsRect(player.frame, object1.frame)) {
[EndGame];
}
}
override func update(currentTime: CFTimeInterval) {
/* Called before each frame is rendered */
}
func addObject() {
let object = SKSpriteNode(imageNamed: "object1”)
object.name = "object1”
object.position = CGPoint(x: size.width/4, y: size.height/4)
self.addChild(object)
}
func addSecondObject() {
let object = SKSpriteNode(imageNamed: "object2”)
object.name = "object2”
object.position = CGPoint(x: size.width/2, y: size.height/2)
self.addChild(object)
}
}
So you can see my collision code is this:
func Collision() {
if (CGRectIntersectsRect(player.frame, object.frame )) {
[EndGame];
}
if (CGRectIntersectsRect(player.frame, object1.frame)) {
[EndGame];
}
}
The problem is that because object and object 1 variables are private to func (addObject) and func (addSecondObject), I can't call them in the above code. When they collide, currently I just want EndGame() to run which prints "Game Over" in the console.
I don't know if the method I have taken for collision detection is correct, but any help would be great! Thanks :)

Answer 1

For very basic sprites, yes, its right. You can imagine a diagonal line image "/" would trigger a collision if the top left corner of it overlapped with something, even though the actual object doesn't overlap.
Apple has a nice page discussing collisions here : https://developer.apple.com/library/ios/documentation/GraphicsAnimation/Conceptual/CodeExplainedAdventure/HandlingCollisions/HandlingCollisions.html
Also, numerous youtube videos talk about how to get this sort of thing working. eg : https://www.youtube.com/watch?v=dX0KvKtc3_w
You need to make it so the collision detection code runs(possible on a timer or something) and then, perhaps, pass in the objects you want to check or make those objects members of the class (IBOutlet) or similar strategy to gain access to them.

Answer 2

You have to use SKPhysicsbody:
struct PhysicsCategory {
static let None : UInt32 = 0
static let Player : UInt32 = 0b1
static let Object : UInt32 = 0b10
}
player.physicsBody = SKPhysicsBody(rectangleOfSize: player.size) // 1
player.physicsBody?.dynamic = true // 2
player.physicsBody?.categoryBitMask = PhysicsCategory.Player// 3
player.physicsBody?.contactTestBitMask = PhysicsCategory.Object//4
player.physicsBody?.collisionBitMask = PhysicsCategory.None // 5
You set the SKPhysicsBody and make it the size of your player-object
Then you make it dynamic. That the physicsbody is dynamic.
That is the categoryBitMask. It's like the identifier of your SKNode. So that other SKNodes can register on you and say: "Hey I want to know if I touch that guy".
That's the contactTestbitMask which handles which SKNodes should interact with you. So you say "If that node touches me, say something".
What should happen, if this node collides.
For more informations and a nice starter tutorial, use raywenderlichs tutorial.