SKSpriteNode showing non integer position when assigned an SKPhysicsBody - ios

Question

I have some very simple Swift code which places an SKSpriteNode on screen at position x:214, y:200. In the update method, I print the current position of said SKSpriteNode. If I omit all of the SKPhysicsBody code, then the position of my SKSpriteNode is shown in the debug window as (214.0, 200.0) which is as I would expect it. If, however, I run the program with the SKPhysicsBody code present, then the first print returns correct with (214.0, 200.0), but subsequent calls return (214.000015258789, 200.0).
This looks to me like something in the physics world is affecting (albeit in a very small way) the position of the SKSpriteNode. What I cannot fathom for the life of me is what that could be. My code is exactly as shown below, nothing more and nothing less. I think I have disabled everything that could possibly have any effect on the position. I am just hoping that I might have missed something silly.
The problem may seem trivial as the values are only fractionally off, however when I attempt to move the sprite smoothly across the screen (incrementing it's x position + 1 on each update) then it will occasionally miss an entire position, going from 289.0 to 289.99, then 291.0.
Any help would be much appreciated. It feels like a bug to me, but as I am fairly new to the physics side of SpriteKit, I would like to be certain.
import SpriteKit
class GameScene: SKScene {
private var playerSprite : SKSpriteNode!
override func didMoveToView(view: SKView) {
self.physicsBody = SKPhysicsBody(edgeLoopFromRect: self.frame)//borderBody
self.physicsWorld.gravity = CGVector(dx: 0, dy: 0)
playerSprite = SKSpriteNode(color: UIColor.yellowColor(), size: CGSize(width: 100, height: 100))
playerSprite.position = CGPoint(x: 214, y: 200)
playerSprite.physicsBody = SKPhysicsBody(rectangleOfSize: CGSize(width: 100, height: 100))
if let playerSpritePhysicsObject = playerSprite.physicsBody {
playerSpritePhysicsObject.usesPreciseCollisionDetection = true
playerSpritePhysicsObject.affectedByGravity = false
playerSpritePhysicsObject.allowsRotation = false
playerSpritePhysicsObject.dynamic = false
playerSpritePhysicsObject.angularVelocity = 0.0
playerSpritePhysicsObject.friction = 0.0
playerSpritePhysicsObject.linearDamping = 0.0
playerSpritePhysicsObject.angularDamping = 0.0
playerSpritePhysicsObject.velocity = CGVectorMake(0, 0)
playerSpritePhysicsObject.restitution = 0.0
}
self.addChild(playerSprite)
}
override func update(currentTime: NSTimeInterval) {
print("playerSprite Position = \(playerSprite.position)")
}
}
Here is the debug window output:
playerSprite Position = (214.0, 200.0)
2017-06-19 20:39:47.682 PhysicsTest[9193:2340365] <SKMetalLayer: 0x14fe6e760>: calling -display has no effect.
playerSprite Position = (214.000015258789, 200.0)
playerSprite Position = (214.000030517578, 200.0)
playerSprite Position = (214.000030517578, 200.0)
playerSprite Position = (214.000030517578, 200.0)
playerSprite Position = (214.000030517578, 200.0)

Answer 1

After some time agonising over this problem, I think I may have found a work around. It's nasty but does the trick. Simply reset the position of the SKSpriteNode in the didFinishUpdate() function which occurs after the didSimulatePhysics() function has complete.
override func didFinishUpdate() {
playerSprite.position.x = 214
}
Having tested further, I found this didn't work for iOS 7.1. In order for it work on older devices, you must place the code in the didSimulatePhysics() function instead:
override func didSimulatePhysics() {
playerSprite.position.x = 214
}