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图像属性。但是为了完成图像部分,我的子类必须是它自己的委托(delegate)并实现 viewForZoomingInScrollView
。
但是当有人使用我的 ScrollView 子类时,他们可能也希望获得委托(delegate)通知以查看 scrollViewDidScroll
或您有什么。
在 Swift 中,我如何获得这两个?
最佳答案
这是此模式的 Swift 版本:
尽管 forwardInvocation:
在 Swift 中被禁用,我们仍然可以使用 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")
}
}
关于swift - 在 Swift 中,我如何拥有一个具有内部和外部委托(delegate)的 UIScrollView 子类?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/26953559/