Creating a sub-class from a node in the GameScene class

Question

I'm trying to make a class from this node so I can make various objects from it, but Xcode keeps saying "Expected Declaration". How can I make a class from my node? Here is the code that's giving me an error: P.S. I am relatively new to StackOverflow, so if my question needs more details please let me know instead of putting it on hold. Thanks!

import SpriteKit
import GameplayKit

class GameScene: SKScene, SKPhysicsContactDelegate  {

    override func didMove(to view: SKView) {

        class nodeClass{
            let platform = SKSpriteNode(color: UIColor.yellow, size: CGSize(width: 400, height: 60))

            platform.xScale = 0.8
            platform.yScale = 0.8
            platform.physicsBody = SKPhysicsBody(rectangleOf: CGSize(width: platform.size.width, height: platform.size.width / 6))

            platform.position = CGPoint(x: 150, y: -100)
            platform.physicsBody?.categoryBitMask = 1
            platform.physicsBody?.collisionBitMask = 0
            platform.physicsBody?.isDynamic = false
            platform.physicsBody?.affectedByGravity = false

            self.addChild(platform)
}
}
}

Answer 1

Ad @Confused just said, you should avoid declaring a class inside a method.

Here's a possible solution

class GameScene: SKScene, SKPhysicsContactDelegate  {

    override func didMove(to view: SKView) {
        let platform = Platform(size: CGSize(width: 400, height: 60))
        platform.xScale = 0.8
        platform.yScale = 0.8
        platform.position = CGPoint(x: 150, y: -100)
        self.addChild(platform)
    }
}

class Platform: SKSpriteNode {

    init(size: CGSize) {
        super.init(texture: nil, color: .yellow, size: size)
        let physicsBody = SKPhysicsBody(rectangleOf: CGSize(width: size.width, height: size.width / 6)) // Are you sure about this??
        physicsBody.categoryBitMask = 1
        physicsBody.collisionBitMask = 0
        physicsBody.isDynamic = false
        physicsBody.affectedByGravity = false
        self.physicsBody = physicsBody
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}