cocoa - 从泛型类传递自引用

Question

我想知道如何从泛型类传递 self 引用。换句话说，如何摆脱以下代码中的 AnyObject ？

protocol StateControllerDelegate: class {

    typealias StateType

    func stateController(stateController: AnyObject, didTransitionFromState fromState: StateType, toState: StateType)

}

class StateController<StateControllerDelegateType: StateControllerDelegate> {

    var delegate: StateControllerDelegateType?

}

谢谢!

Answer 1

试试这个。

protocol StateControllerDelegate: class {

    typealias StateType

    func stateController(stateController: StateController<Self>, didTransitionFromState fromState: StateType, toState: StateType)

    var fromState: StateType { get }
    var   toState: StateType { get }
}

class StateController<StateControllerDelegateType: StateControllerDelegate> {

    var delegate: StateControllerDelegateType?

    func callDelegate() {
        delegate!.stateController(self,
            didTransitionFromState: delegate!.fromState,
                           toState: delegate!.toState)
    }
}

final class MyDelegate: StateControllerDelegate {

    typealias StateType = Int

    func stateController(stateController: StateController<MyDelegate>, didTransitionFromState fromState: StateType, toState: StateType) {
        println("fromState=\(fromState), toState=\(toState)")
    }

    var fromState: StateType { return 0; }
    var   toState: StateType { return 1; }
}


let ctrl = StateController<MyDelegate>()
ctrl.delegate = MyDelegate()
ctrl.callDelegate()

编辑；我想对重要的一点做出解释。

我做了MyDelegate作为final类，因为如果我不这样做，StateController<Self>在MyDelegate的背景下意味着StateController<T> (其中 T 可以是继承 MyDelegate 的任何类型)，所以 StateController<MyDelegate>函数签名不符合StateController<Self> 。目前，Swift 不支持任何协变/逆变之类的功能，因此 StateController<Y>兼容StateController<X> (其中 Y 扩展 X )是不可能的。但是一旦我添加 final上课MyDelegate ，现在StateController<Self>意味着只是 StateController<MyDelegate> (在 MyDelegate 的上下文中)。