Passing Information To A Class On Initialisation - swift

Question

I'm struggling to understand how class initialisation works. From looking at solutions to other problems I have this as an example of the classes in my app.
import Foundation
import SpriteKit
class Ground : SKSpriteNode {
override init(texture: SKTexture!, color: SKColor, size: CGSize) {
super.init(texture: texture, color: color, size: size)
self.zPosition = -20
self.name = "Ground";
}
func configure (size: CGSize, position: CGPoint) {
self.size = size
self.position = position
// Set up the Physics
self.physicsBody = SKPhysicsBody(rectangleOf: size)
self.physicsBody?.contactTestBitMask = PhysicsCategory.Player
self.physicsBody?.categoryBitMask = PhysicsCategory.Ground
self.physicsBody?.collisionBitMask = PhysicsCategory.All
self.physicsBody?.affectedByGravity = false
self.physicsBody?.allowsRotation = false
self.physicsBody?.isDynamic = false
self.physicsBody?.mass = 1.99999
}
convenience init(color: SKColor, isActive: Bool = false) {
let size = CGSize(width: 10, height: 10);
self.init(texture:nil, color: color, size: size)
}
required init?(coder aDecoder: NSCoder) {
// Decoding length here would be nice...
super.init(coder: aDecoder)
}
}
I've put the 'configure' function as a kludge fix to let me pass the scene to the class so I can set sizes depending on the size of the device screen. Ideally I would like to just pull this information on initialisation but everything I try throws up errors that I don't understand.
Im not sure which way would be correct but I was wondering firstly, how would I pass arguments to the class to start with.. e.g..
let myClass = Ground(scene: self)
or can I somehow pull the scene information from directly within the class? I can pass info into functions/methods as I did with 'configure' but I couldn't get it to work on initialisation which would certainly be cleaner.
How would you guys do it?

Answer 1

Size
You should not programmatically change the size of a sprite depending on the current device, just use the same size and then let SpriteKit resizing it for you.
Loading from .sks
This initializer
init?(coder aDecoder: NSCoder)
is used when the Sprite is loaded from a .sks file. However in Xcode 7 you cannot pass values from the .sks to the sprite to set the attributes. I'm not sure you are using a .sks file so for now I am just throwing a fatal_error here. In Xcode 8 however you will be able to pass values from the .sks file to your own class.
required init?(coder aDecoder: NSCoder) {
fatalError("Not implemented")
}
Scene
You don't need to pass a reference of the current scene to your class. Every SKNode has the scene property, just use it to retrieve the scene where the node lives. Of course keep in mind that if you invoke .scene before the node has been added to a scene it will returns nil.
Code
This is the final code
class Ground : SKSpriteNode {
init(color: SKColor = .clearColor(), isActive:Bool = false) {
let texture = SKTexture(imageNamed: "ground")
super.init(texture: texture, color: color, size: texture.size())
self.name = "Ground"
self.zPosition = -20
let physicsBody = SKPhysicsBody(texture: texture, size: texture.size())
physicsBody.contactTestBitMask = PhysicsCategory.Player
physicsBody.categoryBitMask = PhysicsCategory.Ground
physicsBody.collisionBitMask = PhysicsCategory.All
physicsBody.affectedByGravity = false
physicsBody.allowsRotation = false
physicsBody.dynamic = false
physicsBody.mass = 1.99999
self.physicsBody = physicsBody
}
required init?(coder aDecoder: NSCoder) {
fatalError("Not implemented")
}
}

Answer 2

Unless I'm missing something else you're trying to do, you should be able to move the initialization of the PhysicsBody and the other properties from you configure() method and into your init() for the class. Then you can pre-size the texture you pass in on instantiation to result in the proper size for the device.
Also, the position property of the SKSpriteNode can be set by the instantiating class. This means you can accomplish the sizing based on device and the setting of the position property right after instantiating it in your scene and before adding it as a child of the scene.
ADDED:
class Ground : SKSpriteNode {
override init(texture: SKTexture!, color: SKColor, size: CGSize) {
super.init(texture: texture, color: color, size: size)
}
convenience init(texture: String, scene: SKScene, isActive: Bool = false) {
let texture = SKTexture(imageNamed: "\(yourtexturename)")
self.init(texture:teture, color: color, size: scene.size)
self.size = size
self.position = [YOU CAN NOW SET POSITION BASED ON THE SCENE]
self.physicsBody = SKPhysicsBody(rectangleOf: size)
self.physicsBody?.contactTestBitMask = PhysicsCategory.Player
self.physicsBody?.categoryBitMask = PhysicsCategory.Ground
self.physicsBody?.collisionBitMask = PhysicsCategory.All
self.physicsBody?.affectedByGravity = false
self.physicsBody?.allowsRotation = false
self.physicsBody?.isDynamic = false
self.physicsBody?.mass = 1.99999
self.zPosition = -20
self.name = "Ground";
}
required init?(coder aDecoder: NSCoder) {
// Decoding length here would be nice...
super.init(coder: aDecoder)
}
}
You might not need to override the original init() method but I didn't test anything.