Sprite Kit: SKSpriteNode controlled by device motion falls out of the screen in the corners

Question

I am creating a SpriteKit game which uses the CoreMotion framework to move a SKSpriteNode, userNode, around the screen. For the scaling, I have set it to ResizeFill, and have used view.frame to store the four bounds of the view in variables:

//setting screens bounds
    var rightBound = CGFloat()
    var leftBound = CGFloat()
    var upperBound = CGFloat()
    var bottomBound = CGFloat()
    rightBound = view.frame.width - (userNode.size.width / 2)
    leftBound = CGRectGetMinX(view.frame) + (userNode.size.width / 2)
    upperBound = view.frame.height - (userNode.size.height / 2)
    bottomBound = CGRectGetMinY(self.frame) + (userNode.size.height / 2)

To attempt to keep userNode on screen, I created a function to run in the update function:

func keepUserNodeOnScreen(){
    if userNode.position.x >= rightBound{
        userNode.position.x = rightBound

    }
    else if userNode.position.x <= leftBound{
        userNode.position.x = leftBound
    }
    else if userNode.position.y >= upperBound{
        userNode.position.y = upperBound
    }
    else if userNode.position.y <= bottomBound{
        userNode.position.y = bottomBound
    }

}

For some reason, however, when the node reaches the corners of the view, it falls out of the view. I have also tried self.physicsBody = SKPhysicsBody(edgeLoopFromRect(view.frame)), but this didn't work either. What could it be that is causing this?

Edit: Here is the userNode generation code:

    userNode.color = SKColor.redColor()
    userNode.size = CGSizeMake(15, 15)
    userNode.position = CGPointMake(view.frame.size.width / 2, view.frame.size.height / 2)
    userNode.physicsBody = SKPhysicsBody(rectangleOfSize: userNode.size)
    userNode.physicsBody?.dynamic = true
    userNode.physicsBody?.allowsRotation = false
    userNode.physicsBody?.categoryBitMask = userCategory
    userNode.physicsBody?.contactTestBitMask = bulletCategory
    self.addChild(userNode)

Here is the code for moving userNode, set to run in the update function:

func moveUserNode(){
    if motionManager.accelerometerAvailable == true{
        motionManager.deviceMotionUpdateInterval = 0.001

        motionManager.startDeviceMotionUpdatesToQueue(NSOperationQueue.currentQueue(), withHandler:{
            deviceManager, error in
            if self.gameOn == true{
                var roll: CGFloat = CGFloat(self.motionManager.deviceMotion.attitude.roll)
                var pitch: CGFloat = CGFloat(-self.motionManager.deviceMotion.attitude.pitch) + CGFloat(0.6)

                //Keep userNode on screen

                self.newPosition.x = self.userNode.position.x + CGFloat(roll) * 20
                self.newPosition.y = self.userNode.position.y + CGFloat(pitch) * 20
                self.userNode.position = self.newPosition

            }
            else if self.gameOn == false{
                self.motionManager.stopDeviceMotionUpdates()
            }
        })
    }
}

Answer 1

In keepUserNodeOnScreen, your if/else statements aren't testing for all the possible ways userNode can exit the screen. Deleting all of the else statements will resolve this.

An alternative approach is to add an edge-loop

self.physicsBody = SKPhysicsBody(edgeLoopFromRect(view.frame))

and move userNode with applyForce or applyImpulse instead of moving it by changing its position property. SpriteKit does not detect collisions if the node's position is changed, directly.