Unexpectedly Found Nil SKSpriteNode - swift

Question

I get the following error when there's contact between bullet and the plane.
fatal error: unexpectedly found nil while unwrapping an Optional value
Plane Function:
func addPlane() {
var myplane : SKSpriteNode?
myplane = SKSpriteNode(imageNamed: "plane")
let actualY = random(min: 100, max: size.height - myplane!.size.height/2)
myplane!.position = CGPoint(x: size.width + myplane!.size.width/2, y: actualY)
myplane!.physicsBody = SKPhysicsBody(rectangleOfSize: myplane!.size) // 1
myplane!.physicsBody?.dynamic = false // 2
myplane!.physicsBody!.categoryBitMask = CollisionCategoryPowerUpOrbs
myplane!.physicsBody!.collisionBitMask = 0
myplane!.name = "plan"
addChild(myplane!)//
let actualDuration = random(min: CGFloat(2.0), max: CGFloat(4.0))
let actionMove = SKAction.moveTo(CGPoint(x: -myplane!.size.width/2, y: actualY), duration: NSTimeInterval(actualDuration))
myplane!.runAction(SKAction.sequence([actionMove]))
}
When the user touches the screen, it will shoot a bullet with this funciton:
override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
guard let touch = touches.first else {
return
}
let touchLocation = touch.locationInNode(self)
var projectile : SKSpriteNode?
projectile = SKSpriteNode(imageNamed: "bomb")
projectile!.position = CGPoint(x: 50, y: 100.0)
projectile!.physicsBody = SKPhysicsBody(circleOfRadius: projectile!.size.width/2)
projectile!.physicsBody?.dynamic = true
projectile!.physicsBody!.allowsRotation = false
projectile!.physicsBody!.categoryBitMask = CollisionCategoryPlayer
projectile!.physicsBody!.contactTestBitMask = CollisionCategoryPowerUpOrbs
projectile!.physicsBody!.collisionBitMask = 0
projectile!.physicsBody!.linearDamping = 1.0
projectile!.name = "shot"
let offset = touchLocation - projectile!.position
if (offset.x < 0) { return }
addChild(projectile!)
let direction = offset.normalized()
let shootAmount = direction * 1000
let realDest = shootAmount + projectile!.position
let actionMove = SKAction.moveTo(realDest, duration: 2.0)
let actionMoveDone = SKAction.removeFromParent()
projectile!.runAction(SKAction.sequence([actionMove, actionMoveDone]))
}
Function to hide the plane on contact:
func didBeginContact(contact: SKPhysicsContact) {
let nodeB = contact.bodyA.node!
if nodeB.name == "plan" {
nodeB.removeFromParent()
}
}
I call the addPlane function in ViewDidLoad like this:
runAction(SKAction.repeatActionForever(
SKAction.sequence([
SKAction.runBlock(addPlane),
SKAction.waitForDuration(1.5)
])
))

Answer 1

Change you code with a '?' to do a nil check:
func didBeginContact(contact: SKPhysicsContact) {
let nodeB = contact.bodyA.node
if nodeB?.name == "plan" {
nodeB?.removeFromParent()
}
}
This solution will prevent the crash but has the disadvantage that some unnecessary contact events are still triggered.
Removing a node inside didBeginContact should be avoided. This can lead to situations where the node is already removed (nil), but the PhysicsBody is still active.
(see also the comments from KnightOfDragon)