在 Swift 中扩展 SCNNode [英] Extending SCNNode in Swift

问题描述

我想在 Swift 中扩展 SCNNode(如果可能).这是我的尝试:

I would like to extend SCNNode (if possible) in Swift. Here's my attempt:

class MyNode : SCNNode {

    override init(geometry: SCNGeometry) -> SCNNode {
        return super.init(geometry)
    }

    /* Xcode required this */
    required init(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

-> 操作符被标记为错误一行中的连续声明必须用 ; 分隔".

The -> operator is being tagged with an error "Consecutive declarations on a line must be separated by ;".

我知道这是不对的，但如果我幽默 Xcode，它会按如下方式修复"它:

I know this is not right but if I humour Xcode it "fixes" it as follows:

override init(geometry: SCNGeometry); -> SCNNode {

这是无稽之谈，然后Xcode抱怨预期声明".

Which is nonsense and then Xcode complains "Expected declaration".

我不太了解 SCNNode 的实现——如果我在 Xcode 中查看它，它都被声明为抽象的(在注释中)并且不提供任何实现.文档没有建议从 SCNNode 扩展任何东西，你直接实例化它，所以我假设我应该能够扩展它.

I don't quite understand the SCNNode implementation - if I look at it in Xcode it's all declared as abstract (in comments) and offers no implementation. The docs do not suggest anything extends from SCNNode, you instantiate it directly, so I am assuming I should be able to extend it.

推荐答案

您只需:

class MyNode : SCNNode {
    /* Xcode required this */
    required init(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

哪个将从基类继承指定的初始化器.

Which will inherit the designated initialiser from the base class.

如果您想指定自己的带有几何图形的初始化程序，则必须调用基类的指定初始化程序，所以我会说这就是您想要的:

If you want to specify your own initialiser that takes a geometry, you must call a designated initialiser of the base class, so I'd say this would be what you'd want:

class MyNode : SCNNode {
    init(geometry: SCNGeometry) {
        super.init()
        self.geometry = geometry
    }
    /* Xcode required this */
    required init(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

您在 SCNNode.h 代码中看到的初始化程序是从 Objective C 方法 nodeWithGeometry 翻译(我相信是自动的)的初始化程序.我相信这是一个方便的初始化程序，即使它没有特别标记为这样，我个人认为这是自动头文件翻译的错误/限制.文档 特别指出:

The initialiser you're seeing in the SCNNode.h code is an initialiser translated (automatically, I believe) from the Objective C method nodeWithGeometry. I believe this is a convenience initialiser, even though it's not specifically marked as such, which I'd personally say is a bug/limitation of the automatic header file translation. The documentation specifically says:

为了一致性和简单性，Objective-C 工厂方法被映射为 Swift 中的便利初始值设定项.

For consistency and simplicity, Objective-C factory methods get mapped as convenience initializers in Swift.

不要被注释中的abstract这个词弄糊涂了；这是 HeaderDoc 标签，用于方法的简短描述，即抽象"用于摘要或摘要.

Don't be confused by the word abstract in the comments; this is the HeaderDoc tag for a short description of a method, i.e. "abstract" is used in the sense of an abridgement or summary.

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