Unwrapping optional values: PhysicsBody - Swift SpriteKit

问题

So I made some adjustments to the ball in my game and to avoid an unwrapping optional value error, I commmented out the following

//didMoveToView
    self.physicsWorld.gravity = CGVectorMake(0, 0)
    self.physicsWorld.contactDelegate = self
    let fieldBody = SKPhysicsBody.init(edgeLoopFromRect: self.frame)
    self.physicsBody = fieldBody
    self.physicsBody!.affectedByGravity = false
    self.physicsBody!.usesPreciseCollisionDetection = true
    self.physicsBody!.dynamic = true
    self.physicsBody!.mass = 0
    self.physicsBody!.friction = 0
    self.physicsBody!.linearDamping = 0
    self.physicsBody!.angularDamping = 0
    self.physicsBody!.restitution = 1
    self.physicsBody!.categoryBitMask = CollisionTypes.Floor.rawValue
    self.physicsBody!.contactTestBitMask = CollisionTypes.Ball.rawValue

    // Prepare the ball - physics engine.
    ball.physicsBody = SKPhysicsBody(circleOfRadius: ball.frame.width/2)
    ball.physicsBody!.affectedByGravity = true
    ball.physicsBody!.restitution = 0.8
    ball.physicsBody!.linearDamping = 0
    ball.physicsBody!.friction = 0.3
    ball.physicsBody!.dynamic = true
    ball.physicsBody!.mass = 0.5
    ball.physicsBody!.allowsRotation = true
    ball.physicsBody!.categoryBitMask = CollisionTypes.Ball.rawValue
    ball.physicsBody!.contactTestBitMask = CollisionTypes.Floor.rawValue
    ball.physicsBody!.collisionBitMask = CollisionTypes.Floor.rawValue
}

I did that, my game launced but as soon as toucheBegan, the same error popped up. I do not know how to get around all of these unrwapping errors. I am new to swift and not sure how i should adjust thse physics. My contactBegin looks this:

func didBeginContact(contact: SKPhysicsContact) {
    let bitMaskAAndB = contact.bodyA.categoryBitMask == CollisionTypes.Floor.rawValue &&
                contact.bodyB.categoryBitMask == CollisionTypes.Ball.rawValue
    let ballAndBoardMask = CollideType.Ball.toMask() | boards.usedCollideMasks

    // ball and board, handle it by board delegate
    if bitMaskAAndB | ballAndBoardMask == ballAndBoardMask {

        let boardNode: SKNode! = contact.bodyA.categoryBitMask == CollideType.Ball.toMask() ? contact.bodyB.node : contact.bodyA.node
        let board = boardNode.bind as! BoardDelegate
        board.didBeginContact(boardNode, ball: ball, contact: contact, game: self)
    }

    // ball and ceil => stop game
    else if bitMaskAAndB == CollideType.toMask([.Ball, .Ceil]) {
        stopGame()
    }

    // ball and floor => stop game add explosion or fall off screen
    else if bitMaskAAndB == CollideType.toMask([.Ball, .Floor]) {
        stopGame()
    }
}
func didEndContact(contact: SKPhysicsContact) {

    let ballAndBoardMask = CollideType.Ball.toMask() | boards.usedCollideMasks

    // ball and board, handle it by board delegate
    if contact.bodyA.categoryBitMask | contact.bodyB.categoryBitMask | ballAndBoardMask == ballAndBoardMask {

        let boardNode: SKNode! = contact.bodyA.categoryBitMask == CollideType.Ball.toMask() ? contact.bodyB.node : contact.bodyA.node
        let board = boardNode.bind as! BoardDelegate
        board.didEndContact(boardNode, ball: ball, contact: contact, game: self)
    }

}

EDIT: I set up my physics world to the suggestions you made and adjusted my didBeginContact fun however with the following code, I am getting multiple errors regarding: cannot convert value of type bool to UInt32.

PS. thank you for your help and patience, this is all new terminology and Im doing my best to understand. :)

回答1:

I don't know your CollideType class or declaration, so my code below explain to you how to build a correct physicsWorld and physicsBody to don't have issues during the collisions.

But first: we're going to be using the categoryBitMask, contactTestBitMask and collisionBitMask properties in their fullest for this project, because we have very precise rules that make the project work:

categoryBitMask is a number defining the type of object this is for considering collisions.
collisionBitMask is a number defining what categories of object this node should collide with.
contactTestBitMask is a number defining which collisions we want to be notified about.

SpriteKit expects these three bitmasks to be described using a UInt32.Your bitmasks should start at 1 then double each time.

The code:

class GameScene: SKScene, SKPhysicsContactDelegate {
    var ball: Ball!
    let ballSpeedX = CGFloat(500)
    enum CollisionTypes: UInt32 {
        case Field = 1
        case Ball = 2
    }
    override func didMoveToView(view: SKView) {
        // ball
        ball = Ball(imageNamed:"colorBall.png")
        ball.position = CGPointMake(self.ball.frame.size.width,self.ball.frame.size.height)

        // Prepare the world - physics engine.
        self.physicsWorld.gravity = CGVectorMake(0, -6)
        self.physicsWorld.contactDelegate = self
        let fieldBody = SKPhysicsBody.init(edgeLoopFromRect: self.frame)
        self.physicsBody = fieldBody
        self.physicsBody!.affectedByGravity = false
        self.physicsBody!.usesPreciseCollisionDetection = true
        self.physicsBody!.dynamic = true
        self.physicsBody!.mass = 0
        self.physicsBody!.friction = 0
        self.physicsBody!.linearDamping = 0
        self.physicsBody!.angularDamping = 0
        self.physicsBody!.restitution = 1
        self.physicsBody!.categoryBitMask = CollisionTypes.Field.rawValue
        self.physicsBody!.contactTestBitMask = CollisionTypes.Ball.rawValue

        // Prepare the ball - physics engine.
        ball.physicsBody = SKPhysicsBody(circleOfRadius: ball.frame.width/2)
        ball.physicsBody!.affectedByGravity = true
        ball.physicsBody!.restitution = 0.8
        ball.physicsBody!.linearDamping = 0
        ball.physicsBody!.friction = 0.3
        ball.physicsBody!.dynamic = true
        ball.physicsBody!.mass = 0.5
        ball.physicsBody!.allowsRotation = true
        ball.physicsBody!.categoryBitMask = CollisionTypes.Ball.rawValue
        ball.physicsBody!.contactTestBitMask = CollisionTypes.Field.rawValue
        ball.physicsBody!.collisionBitMask = CollisionTypes.Field.rawValue

        //ball.physicsBody!.categoryBitMask = CollideType.Ball.toMask()
        //ball.physicsBody!.collisionBitMask = CollideType.toMask([.Scene, .Ceil, .Floor]) | boards.usedCollideMasks
        //ball.physicsBody!.contactTestBitMask = CollideType.toMask([.Scene, .Ceil, .Floor]) | boards.usedCollideMasks
        ball.hidden = false
        self.addChild(ball)
    }
    func didBeginContact(contact: SKPhysicsContact) {
        if (contact.bodyA.categoryBitMask == CollisionTypes.Field.rawValue &&
            contact.bodyB.categoryBitMask == CollisionTypes.Ball.rawValue) {
            print("contact between field and ball")
        }
    }
}

As you can see, the first important thing is to prepare the physicsWorld (track the boundaries within wich your physics must work), assign it a category and all the other parameters need to interact with the other objects. Then you build the physicsBody of your object , in this case the ball.

来源：https://stackoverflow.com/questions/38280426/unwrapping-optional-values-physicsbody-swift-spritekit

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