didBeginContact works without contact swift - cocoa

Question

I'm writing SpriteKit app for Mac OS. I have two objects (projectile and a monster):
let suric = SKSpriteNode(imageNamed: "projectile.png")
suric.position = player.position
suric.physicsBody = SKPhysicsBody(circleOfRadius: self.size.width / 2)
suric.physicsBody?.categoryBitMask = Detection.suric
suric.physicsBody?.collisionBitMask = Detection.no
suric.physicsBody?.contactTestBitMask = Detection.monster
suric.physicsBody?.usesPreciseCollisionDetection = true
suric.physicsBody?.dynamic = true
let offset = location - suric.position
if offset.x < 0 {
return
}
addChild(suric)
let direc = offset.normalized()
let shoot = direc * 1000
let dest = shoot + suric.position
let move = SKAction.moveTo(dest, duration: 2.0)
let stop = SKAction.removeFromParent()
suric.runAction(SKAction.sequence([move, stop]))
Monster code:
let monster = SKSpriteNode(imageNamed: "monster.png")
let y = random(min: monster.size.height / 2, size.height - monster.size.height)
monster.position = CGPoint(x: self.size.width + monster.size.width / 2, y: y)
monster.physicsBody = SKPhysicsBody(rectangleOfSize: monster.size)
monster.physicsBody?.usesPreciseCollisionDetection = true
monster.physicsBody?.categoryBitMask = Detection.monster
monster.physicsBody?.contactTestBitMask = Detection.suric
monster.physicsBody?.collisionBitMask = Detection.no
monster.physicsBody?.dynamic = true
addChild(monster)
let duration = random(min: 2.0, 4.0)
let move = SKAction.moveTo(CGPoint(x: -monster.size.width / 2, y: y), duration: NSTimeInterval(duration))
let done = SKAction.removeFromParent()
monster.runAction(SKAction.sequence([move, done]))
Detection structure:
struct Detection {
static var no : UInt32 = 0
static var all : UInt32 = UInt32.max
static var monster : UInt32 = 0b1
static var suric : UInt32 = 0b10
}
And then I try to check if there was a contact between these 2 objects:
func didBeginContact(contact: SKPhysicsContact) {
var first : SKPhysicsBody
var second : SKPhysicsBody
if contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask {
first = contact.bodyA
second = contact.bodyB
}
else {
first = contact.bodyB
second = contact.bodyA
}
if (first.categoryBitMask & Detection.monster != 0) && (second.categoryBitMask & Detection.suric != 0) {
suricHit(first.node as? SKSpriteNode, monster: second.node as? SKSpriteNode)
}
}
It works even if they didn't actually make a contact. E.g., the projectile is near the top of the window, the monster is at the bottom, but this function works.
EDIT:
I added this code to didBeginContact:
let nodeA = (first.node as! SKSpriteNode)
let nodeB = (second.node as! SKSpriteNode)
println("\(nodeA.position)\t\(nodeA.size)")
println("\(nodeB.position)\t\(nodeB.size)")
println((contact.contactPoint))
println()
The example of out:
(510.201293945312, 285.025665283203) (54.0, 80.0)
(532.54345703125, 378.878845214844) (20.0, 20.0)
(852.469543457031, 530.415222167969)
As you can see, the x position of nodes are 510 and 532, but the contact x point is 852. I just have no idea how and why. Does anybody have a solution?

Answer 1

You're missing an extra set of parenthesis in the if statement.
if ((first.categoryBitMask & Detection.monster != 0) && (second.categoryBitMask & Detection.suric != 0)) {
suricHit(first.node as? SKSpriteNode, monster: second.node as? SKSpriteNode)
}
PS I followed this tutorial and put my project on GitHub, check it out!