ios - Sprite 套件 | swift 3 | - 无法转换 Void 类型的值(又名“( )' to expected argument type ' unsafeRawPointer”

Question

无法将 Void 类型的值(又名“()”)转换为预期的参数类型“unsafeRawPointer”

代码允许我通过触摸在屏幕上画线。我正在使用字典来允许多个用户同时绘制多条线。

就在我试图将指针存储在 NSValue 键中时。

在我开始升级到 Swift 3 之前，这在 Objective C 中运行良好。

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
        }
    }
}

有谁知道我为什么会收到这个错误以及如何解决该错误？

Answer 1

也许您混淆了 (void *)... 在 Objective-C 中的转换和 as! Swift 中的 Void。它们完全不同。

由于 UITouch 是 Hashable，您可以将它用作 Swift Dictionary 的键。尝试使用它:

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
        }
    }
}

我不知道 UITouch 的这种用法，但正如您所说的使用 NSValue 的 Objective-C 版本确实有效，我上面的代码应该有效。