Swift 链接选项

Question

我正在运行 Yosemite 公测版和 Xcode6 Beta 4

基于 OSX SceneKit 模板，我试图确定单击了哪个节点。这是 mouseDown 函数，主要来自模板代码。

标记为 #1 的注释有效，如果它很好，但我试图理解为什么代码注释 #2、#3 和 #4 无法编译，或者这些错误真正告诉我的是什么。

搜索错误我没有找到似乎适用于我的案例的结果。

#2 的错误似乎通常适用于类型转换，我不认为这里有任何类型转换。

#3 的错误让我完全迷失了方向。

#4 的错误似乎是 SCNNode 没有名称属性，但它确实有。

override func mouseDown(theEvent: NSEvent) {
    /* Called when a mouse click occurs */

    // check what nodes are clicked
    let p = gameView.convertPoint(theEvent.locationInWindow, fromView: nil)
    let hitResults = gameView.hitTest(p, options: nil)

    // check that we clicked on at least one object
    if (hitResults.count > 0){

        // retrieved the first clicked object
        let result: AnyObject = hitResults[0]

// #1 This works
        if let myNode: SCNNode = result.node? {
            if myNode.name? == "Die" {
                println("Node is named Die")
            }
        }

// #2 This does not work
        // error: Could not find an overload for the 'node' that accepts the supplied arguments
        if let myNode = result.node? {
            if myNode.name? == "Die" {
                println("Node is named Die")
            }
        }

// #3 This does not work either
        // error: Type 'String?' does not confrom to protocol '_RawOptionSet'
        if result.node?.name? == "Die" {
            println("Node is named Die")
        }

// #4 This does not work either
        // error: 'SCNNode!' does not have a member named 'name'
        if let myName = result.node?.name? {
            if myName == "Die" {
                println("Node is named Die")
            }
        }

        // get its material
        let material = result.node!.geometry.firstMaterial;

        // highlight it
        SCNTransaction.begin()
        SCNTransaction.setAnimationDuration(0.5)

        // on completion - unhighlight
        SCNTransaction.setCompletionBlock() {
            SCNTransaction.begin()
            SCNTransaction.setAnimationDuration(0.5)

            material.emission.contents = NSColor.blackColor()

            SCNTransaction.commit()
        }

        material.emission.contents = NSColor.redColor()

        SCNTransaction.commit()

    }

    super.mouseDown(theEvent)
}

Answer 1

#2、#3、#4的失败都是因为缺少类型。你说:

the error for #2 seems to usually apply to type casting, and I wouldn't think there is any type casting going on here.

但是，当您尝试将其作为 SCNNode 访问时，您将 result 声明为 AnyObject，因此肯定存在某种类型转换这需要发生。

我以前在使用字典时也见过这种情况。我不仅明确了类型，还预先测试了类型:

var item: AnyObject? = nil
item = map["SWLFlexFormat"]
if let value: AnyObject = item {
    configuration.formatter = getConfiguredFlexFormatter(configuration, item: value);
}

func getConfiguredFlexFormatter(configuration: LoggerConfiguration, item: AnyObject) -> LogFormatter? {
    if let formatString: String = item as? String {
        var formatter = FlexFormatter.logFormatterForString(formatString);
        return formatter
    }
    return nil
}