spritekit collision detection inconsistency (failing to get position of both nodes) - swift

Question

Within didBeginContact function I'm successfully capturing the collision between a horizontal grid line and a circle.
At the collision I can successfully get the position of the circle(head).
if let headBody = contact.bodyB.node as? SnakeBodyUnit {
print("head position ", headBody.position)
}
This successfully prints out:
head position (87.536979675293, 267.116882324219)
Now if I try to examine the horizontal line:
if let tripRow = contact.bodyA.node as? HeadTripper {
print("row position ", tripRow.position)
}
I get the following error:
po tripRow
error: :1:1: error: use of unresolved identifier 'tripRow'
tripRow
Here is the condition where this detection fires:
if (contact.bodyA.categoryBitMask == ColliderType.TripRow && contact.bodyB.categoryBitMask == ColliderType.Head) {
//contact successfully fires
}
The HeadTripper class and the SnakeBodyUnit class are both SKNode classes.
Here is the SnakeBodyUnit class:
import SpriteKit
class SnakeBodyUnit : SKNode {
var bodyDir: Direction?
var id = -1
var staticIDref = -1
var partX:CGFloat = -1
var partY:CGFloat = -1
var bodyT = -1
var staticTurn: TurnCrumb?
var turnRequested = 0
var requestedTurn: Direction?
var unitHolder: SKSpriteNode?
init(size: CGSize, bodyType: Int) {
super.init()
bodyT = bodyType
let reducedSize = size.width
unitHolder = SKSpriteNode()
unitHolder!.size = CGSize(width: (size.width), height: (size.height))
if (bodyT == 0) {
//head
unitHolder!.color = UIColor.clearColor()
//unitHolder!.position = CGPoint(x:xPos, y:yPos);
let shape = SKShapeNode(circleOfRadius: reducedSize/2)
shape.fillColor = UIColor.whiteColor()
shape.strokeColor = UIColor.whiteColor()
shape.position = CGPoint(x: reducedSize/2, y: reducedSize/2)
unitHolder!.addChild(shape)
self.physicsBody = SKPhysicsBody(rectangleOfSize: CGSizeMake(reducedSize, reducedSize), center: CGPointMake(reducedSize/2, reducedSize/2))
self.physicsBody?.affectedByGravity = false
self.physicsBody?.categoryBitMask = ColliderType.Head
self.physicsBody?.dynamic = false
self.physicsBody?.contactTestBitMask = ColliderType.TripRow | ColliderType.TripColumn | ColliderType.Food | ColliderType.Body | ColliderType.WallLeft | ColliderType.WallRight | ColliderType.WallBottom | ColliderType.WallTop | ColliderType.Canvas
} else if (bodyT == 1) {
//body part
self.physicsBody = SKPhysicsBody(rectangleOfSize: CGSizeMake(reducedSize, reducedSize), center: CGPointMake(reducedSize/2, reducedSize/2))
self.physicsBody?.affectedByGravity = false
self.physicsBody?.categoryBitMask = ColliderType.Body
self.physicsBody!.collisionBitMask = 0
self.physicsBody?.dynamic = true
self.physicsBody?.contactTestBitMask = ColliderType.WallLeft | ColliderType.WallRight | ColliderType.WallBottom | ColliderType.WallTop | ColliderType.BodyStatic
} else if (bodyT == 2) {
//static corner
self.physicsBody = SKPhysicsBody(rectangleOfSize: CGSizeMake(reducedSize/2, reducedSize/2), center: CGPointMake(reducedSize/2, reducedSize/2))
self.physicsBody?.affectedByGravity = false
self.physicsBody?.categoryBitMask = ColliderType.BodyStatic
self.physicsBody!.collisionBitMask = 0
self.physicsBody?.dynamic = true
}
unitHolder!.anchorPoint = CGPoint(x: 0, y: 0)
self.addChild(unitHolder!)
}
func updateColor(color: UIColor) {
unitHolder!.color = color
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
//fatalError("init coder not implemented")
}
}
Here is the HeadTripper class:
import SpriteKit
class HeadTripper : SKNode {
var id = -1
var rowTripLine: SKSpriteNode?
var colTripLine: SKSpriteNode?
init(size: CGSize, rowOrCol: Int) {
//init(size: CGSize, xPos: Double, yPos: Double, rowOrCol: Int) {
super.init()
//row 0
//col 1
if (rowOrCol == 0) {
//row
rowTripLine = SKSpriteNode()
rowTripLine!.color = UIColor.redColor()
//rowTripLine!.position = CGPoint(x: 0, y: yPos);
rowTripLine!.size = CGSize(width: Int(size.width), height: 1)
//borderLeft!.physicsBody = SKPhysicsBody(rectangleOfSize: size, center: CGPointMake(reducedSize/2, reducedSize/2))
rowTripLine!.physicsBody = SKPhysicsBody(rectangleOfSize: rowTripLine!.size, center: CGPointMake(rowTripLine!.size.width/2, rowTripLine!.size.height/2))
rowTripLine!.physicsBody?.affectedByGravity = false
rowTripLine!.physicsBody?.categoryBitMask = ColliderType.TripRow
rowTripLine!.physicsBody!.collisionBitMask = 0
rowTripLine!.physicsBody?.dynamic = true
rowTripLine!.anchorPoint = CGPoint(x: 0, y: 0)
self.addChild(rowTripLine!)
} else {
//col
colTripLine = SKSpriteNode()
colTripLine!.color = UIColor.redColor()
//colTripLine!.position = CGPoint(x: xPos, y: 0);
colTripLine!.size = CGSize(width: 1, height: Int(size.height))
//borderLeft!.physicsBody = SKPhysicsBody(rectangleOfSize: size, center: CGPointMake(reducedSize/2, reducedSize/2))
colTripLine!.physicsBody = SKPhysicsBody(rectangleOfSize: colTripLine!.size, center: CGPointMake(colTripLine!.size.width/2, colTripLine!.size.height/2))
colTripLine!.physicsBody?.affectedByGravity = false
colTripLine!.physicsBody?.categoryBitMask = ColliderType.TripColumn
colTripLine!.physicsBody!.collisionBitMask = 0
colTripLine!.physicsBody?.dynamic = true
colTripLine!.anchorPoint = CGPoint(x: 0, y: 0)
self.addChild(colTripLine!)
}
}
required init?(coder aDecoder: NSCoder) {
fatalError("init coder not implemented")
}
}
I generate the HeadTripper lines like this in the main scene:
for var i = 0; i < rowCount; i++ {
let rowTrip = HeadTripper(size: size, rowOrCol: 0)
rowTrip.id = i
rowTrip.position.x = 0
rowTrip.position.y = CGFloat(yVal)
self.addChild(rowTrip)
rowLines.append(CGFloat(rowTrip.position.y))
CGPathMoveToPoint(linePath, nil, 0, CGFloat(yVal))
CGPathAddLineToPoint(linePath, nil, CGFloat(theGrid.screenWidth), CGFloat(yVal))
yVal += (theGrid.snakeHigh + yValPad)
}
Here is how the collider types are setup:
struct ColliderType {
static let Head: UInt32 = 0
static let Food: UInt32 = 0b1
static let Body: UInt32 = 0b10
static let BodyStatic: UInt32 = 0b100
static let WallLeft: UInt32 = 0b1000
static let WallBottom: UInt32 = 0b10000
static let WallRight: UInt32 = 0b100000
static let WallTop: UInt32 = 0b1000000
static let None: UInt32 = 0b10000000
static let Canvas: UInt32 = 0b100000000
static let TripColumn: UInt32 = 0b1000000000
static let TripRow: UInt32 = 0b10000000000
}
The tripRow let setup happens on line 310. On line 309 I can see the contact.bodyA:
0x000000012758db20
{
NSObject = {
isa = 0x000000012758db20
}
_representedObject = 0x00000001275765a0
_field = 0x0000000000000000
_dynamicType = 2
_world = 0x0000000127761b90
_joints = 0x0000000127576270 "0 values"
_inUse = true
_shapeType = 2
_radius = 0
_edgeRadius = 0.0010000000474974513
_mask = 0x0000000000000000
_isPinned = false
_allowsRotation = true
_postStepBlock = 0x000000019e666c70
}
I can also see the contact.bodyA.node:
0x00000001275765a0
{
UIKit.UIResponder = {...}
}
Line 311 never gets called because its in the if condition that isn't passing.
At line 313 I attempt to look at tripRow and get this:
(lldb) po tripRow
error: <EXPR>:1:1: error: use of unresolved identifier 'tripRow'
tripRow
It sounds like issue is related to the children within HeadTripper. I have named the children "row" and "col" respectively.
print("body A name ", contact.bodyA.node?.name)
let tripRow = contact.bodyA.node as? SKSpriteNode
This gives a name of "row". Also tripRow now prints out as:
(lldb) po tripRow
0x0000000155e737c0
{
SpriteKit.SKNode = {...}
}
I think this is very close. The problem still exists that the position is not accurate. The y value should be a number like 54 and it is zero:
(lldb) po tripRow?.position
(x = 0, y = 0)

Answer 1

This was resolved by having just 1 SKSpriteNode referenced in the HeadTripper SKNode class instead of 2.