Spritekit | SWIFT 3 | - Cannot convert value of type Void (aka'()' to expected argument type 'unsafeRawPointer'

Question

Cannot convert value of type Void (aka'()' to expected argument type 'unsafeRawPointer'

The code allows me to draw lines on the screen by touch. I am using a dictionary to allow multiple the user to draw multiple lines simultaneously.

Its just when I am trying to store the pointers in a NSValue key.

This was working fine in Objective C before I started upgrading to Swift 3.

var lines: NSMutableDictionary! 

override func didMove(to view: SKView) {
    lines = NSMutableDictionary.init(capacity: 4)
}

 override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {        
    for t in touches {
        let location: CGPoint = t.location(in: self)
        // Create a mutable path
        let path: UIBezierPath = UIBezierPath()
        path.move(to: location)
        // Create a shape node using the path
        lineNode = SKShapeNode(path: path.cgPath)
        lineNode.name = "sprite\(i)"
        self.addChild(lineNode)

        // Use touch pointer as the dictionary key. Since the dictionary key must conform to
        // NSCopying, box the touch pointer in an NSValue
        var key = NSValue(pointer: (t as! Void))  -- **ERROR HERE**
        lines[key] = lineNode 
    }
}

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
    for t in touches {
        let location = t.location(in: self)

         // Retrieve the shape node that corresponds to touch
         let key = NSValue(pointer: (touches as! Void))  -- **ERROR HERE**
         lineNode = (lines[key] as! String)

        if lineNode != nil {
            // Create and initial a mutable path with the lineNode's path
            let path = UIBezierPath(cgPath: lineNode.path!)
            // Add a line to the current touch point
            path.addLine(to: location)
            // Update lineNode
            lineNode.path = path.cgPath
            lineNode.physicsBody = SKPhysicsBody(edgeChainFrom: path.cgPath)
            lineNode.name = lineNodeCategoryName
        }
    }
}

Does anybody know why I am getting this and how I can resolve the error ?

OOPer OOPer · Accepted Answer · 2016-09-22T10:23:30

Maybe you are confusing (void *)... casting in Objective-C and as! Void in Swift. They are completely different.

As UITouch is Hashable, you can use it as a Key of Swift Dictionary. Try using it:

var lines: [UITouch: SKShapeNode] = [:]

override func didMove(to view: SKView) {
    lines = Dictionary(minimumCapacity: 4)
}

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    for t in touches {
        let location: CGPoint = t.location(in: self)
        // Create a mutable path
        let path: UIBezierPath = UIBezierPath()
        path.move(to: location)
        // Create a shape node using the path
        let lineNode = SKShapeNode(path: path.cgPath)
        lineNode.name = "sprite\(i)"
        self.addChild(lineNode)

        lines[t] = lineNode
    }
}

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
    for t in touches {
        let location = t.location(in: self)

        // Retrieve the shape node that corresponds to touch
        if let lineNode = lines[t] {
            // Create and initial a mutable path with the lineNode's path
            let path = UIBezierPath(cgPath: lineNode.path!)
            // Add a line to the current touch point
            path.addLine(to: location)
            // Update lineNode
            lineNode.path = path.cgPath
            lineNode.physicsBody = SKPhysicsBody(edgeChainFrom: path.cgPath)
            lineNode.name = lineNodeCategoryName
        }
    }
}

I didn't know this usage of UITouch, but as you say your Objective-C version using NSValue actually works, my code above should work.

Spritekit | SWIFT 3 | - Cannot convert value of type Void (aka'()' to expected argument type 'unsafeRawPointer'

1 Answers