在Swift中，我如何拥有一个具有内部和外部委托的UIScrollView子类？

问题描述

我将 UIScrollView 子类化，以添加一些功能，例如双击缩放和用于图库目的的image属性。但是为了做图像部分，我的子类必须是自己的委托并实现 viewForZoomingInScrollView 。

I'm subclassing UIScrollView to add some features such as double tap to zoom and an image property for gallery purposes. But in order to do the image part my subclass has to be its own delegate and implement the viewForZoomingInScrollView.

但是那么当有人使用我的滚动视图子类时，他们可能还希望获得委托通知，以查看 scrollViewDidScroll 或您拥有的东西。

But then when someone uses my scroll view subclass, they might like to get delegate notifications as well to see scrollViewDidScroll or what have you.

在Swift中，我如何同时获得这两个？

In Swift, how do I get both of these?

推荐答案

以下是此模式的Swift版本：

Here is a Swift version of this pattern:

尽管 forwardInvocation：在Swift中已禁用，但我们仍然可以使用

Although forwardInvocation: is disabled in Swift, we can still use forwardingTargetForSelector:

class MyScrollView: UIScrollView {

    class _DelegateProxy: NSObject, UIScrollViewDelegate {
        weak var _userDelegate: UIScrollViewDelegate?

        override func respondsToSelector(aSelector: Selector) -> Bool {
            return super.respondsToSelector(aSelector) || _userDelegate?.respondsToSelector(aSelector) == true
        }

        override func forwardingTargetForSelector(aSelector: Selector) -> AnyObject? {
            if _userDelegate?.respondsToSelector(aSelector) == true {
                return _userDelegate
            }
            else {
                return super.forwardingTargetForSelector(aSelector)
            }
        }

        func viewForZoomingInScrollView(scrollView: MyScrollView) -> UIView? {
            return scrollView.viewForZooming()
        }

        // Just a demo. You don't need this.
        func scrollViewDidScroll(scrollView: MyScrollView) {
            scrollView.didScroll()
            _userDelegate?.scrollViewDidScroll?(scrollView)
        }
    }

    private var _delegateProxy =  _DelegateProxy()

    required init(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        super.delegate = _delegateProxy
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        super.delegate = _delegateProxy
    }

    override var delegate:UIScrollViewDelegate? {
        get {
            return _delegateProxy._userDelegate
        }
        set {
            self._delegateProxy._userDelegate = newValue;
            /* It seems, we don't need this anymore.
            super.delegate = nil
            super.delegate = _delegateProxy
            */
        }
    }

    func viewForZooming() -> UIView? {
        println("self viewForZooming")
        return self.subviews.first as? UIView // whatever
    }

    func didScroll() {
        println("self didScroll")
    }
}

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