Nodes position within scene size - swift

Question

In my SKScene, I am making a simple space shooter game. How can I make sure that my enemies always appear within the screen size regardless of which iphone the game is played at?
In other words words, how do I calculate the max and min X-coordinates of the scene size and more importantly how do i know what's the current scene size depending on which iphone the game is run at?

Answer 1

Don't resize your scene depend by iPhone model, leave Sprite-kit do this kind of job:
scene.scaleMode = SKSceneScaleMode.ResizeFill
The scene is not scaled to match the view. Instead, the scene is
automatically resized so that its dimensions always matches those of
the view.
About the size, when a scene is first initialized, its size property is configured by the designated initializer. The size of the scene specifies the size of the visible portion of the scene in points. This is only used to specify the visible portion of the scene.
Update to help you in positioning:
If you want to set your positions instead to use scaleMode you can
set your scene.scaleMode to .AspectFill for this to work on all scenes and the scene size has to be 2048x1536 or 1536x2048. This will make it scaleable for iPad too.
class StartScene: SKScene {
let playableArea: CGRect!
}
override init(size: CGSize) {
//1. Get the aspect ratio of the device
let deviceWidth = UIScreen.mainScreen().bounds.width
let deviceHeight = UIScreen.mainScreen().bounds.height
let maxAspectRatio: CGFloat = deviceWidth / deviceHeight
//2. For landscape orientation, use this
let playableHeight = size.width / maxAspectRatio
let playableMargin = (size.height - playableHeight) / 2.0
playableArea = CGRect(x: 0, y: playableMargin, width: size.width, height: playableHeight)
//3. For portrait orientation, use this
let playableWidth = size.height / maxAspectRatio
let playableMargin = (size.width - playableWidth) / 2.0
playableArea = CGRect(x: playableMargin, y: 0, width: playableWidth, height: size.height)
super.init(size: size)
}
So you can positioning your object with:
ball.position = CGPoint(x: CGRectGetMidX(playableArea), y: CGRectGetMaxY(playableArea) - (ball.size.height * 0.90))
This code works in the iPhone 4S, 5, 5S, 6, 6 Plus, 6S, 6S Plus, and iPads.
If you want to see your borders (for debug or not):
func drawWorkArea() {
let shape = SKShapeNode()
let path = CGPathCreateMutable()
CGPathAddRect(path, nil, workArea)
shape.path = path
shape.strokeColor = SKColor.redColor()
shape.lineWidth = 8
addChild(shape)
}