EXC_BAD_ACESS crash in SpriteKit on iOS8 - ios

Question

I am getting a very strange crash while trying to change the position of an SKSpriteNode. This crash happens in iOS8 and not in iOS9.
// if the powerup is full, spawn the icon on screen
if orangeBallsCollected == numberOfBallsRequiredToActivatePowerup {
// add the powerup icon to the array of powerupiconsonscreen
powerupIconsOnScreen.append(fewerColorsPowerupIcon)
// set the lighting mask of the powerup icon so that we know what positon it is onscreen for alter
fewerColorsPowerupIcon.lightingBitMask = UInt32(powerupIconsOnScreen.count - 1)
// remove the ball from its current parent
fewerColorsPowerupIcon.removeFromParent()
print(fewerColorsPowerupIcon, fewerColorsPowerupIcon.parent, fewerColorsPowerupIcon.physicsBody, fewerColorsPowerupIcon.superclass)
// place the ball of the screen so that we can bring it on later
fewerColorsPowerupIcon.position = CGPointMake((width * -0.1) , (height * -0.1))
// set the size of the icon
fewerColorsPowerupIcon.xScale = scaleFactor
fewerColorsPowerupIcon.yScale = scaleFactor
// add it the scene
self.addChild(fewerColorsPowerupIcon)
// animate it moving down to the first avaliable position
let animation = SKAction.moveTo(CGPoint(x: width * 0.1, y: height * 0.1), duration: 0.5)
// run the animation!
fewerColorsPowerupIcon.runAction(animation)
// activate the poweurp
activateFewerColors()
}
The crash happens when I try to set the position (fewerColorsPowerupIcon.position) and this is the crash message:
Thread 1: EXC_BAD_ACCESS(code=EXC_I386_GPFLT)
This crash still happens if I put the .removeFromParent() piece of code after I set the position of the node.

Answer 1

I think that if you remove the sprite, you can't do anithing.
so try to do this:
let spriteCopy = fewerColorsPowerupIcon.copy()
// place the ball of the screen so that we can bring it on later
spriteCopy.position = CGPointMake((width * -0.1) , (height * -0.1))
// set the size of the icon
spriteCopy.xScale = scaleFactor
spriteCopy.yScale = scaleFactor
// add it the scene
self.addChild(spriteCopy)
or you can first add in the scene and after change property:
// remove the ball from its current parent
fewerColorsPowerupIcon.removeFromParent()
// add it the scene
self.addChild(fewerColorsPowerupIcon)
// place the ball of the screen so that we can bring it on later
fewerColorsPowerupIcon.position = CGPointMake((width * -0.1) , (height * -0.1))
// set the size of the icon
fewerColorsPowerupIcon.xScale = scaleFactor
fewerColorsPowerupIcon.yScale = scaleFactor

Answer 2

If fewerColorsPowerupIcon were declared something like:
weak var fewerColorsPowerupIcon: Type!
Then as soon as you call removeFromParent(), there might be no strong references to it any more. If that were so, you are not guaranteed that fewerColorsPowerupIcon will be set to nil or that it would be detected. The next time you use it, you might get EXC_BAD_ACCESS.
One way to find something like this is to use the zombie instrument. Under it, no objects are really freed when they have no references, but they complain if you try to use them once all strong references are released.
Another option is to change the ! to ? (and update the code that uses the var). It might be a pain, but there are more guarantees about how ? acts.