不支持用作符合协议 AnyObject 的具体类型

问题描述

我使用 Swift 2 并使用 Wea​​kContainer 作为存储一组弱对象的方式，很像 NSHashTable.weakObjectsHashTable()

I'm using Swift 2 and using WeakContainer as a way to store a set of weak objects, much like NSHashTable.weakObjectsHashTable()

struct WeakContainer<T: AnyObject> {
    weak var value: T?
}

public protocol MyDelegate : AnyObject {

}

然后在我的 ViewController 中，我声明

Then in my ViewController, I declare

public var delegates = [WeakContainer<MyDelegate>]

这是错误的

不支持使用 MyDelegate 作为符合 AnyObject 协议的具体类型

我看到错误是 WeakContainer 有 value 成员声明为 weak，所以 T 是预期的成为对象.但我也将 MyDelegate 声明为 AnyObject.如何解决这个问题?

I see that the error is that WeakContainer has value member declared as weak, so T is expected to be object. But I also declare MyDelegate as AnyObject, too. How to get around this?

推荐答案

我有同样的想法，用泛型创建弱容器.
因此，我为 NSHashTable 创建了包装器，并为您的编译器错误做了一些解决方法.

I had the same idea to create weak container with generics.
As result I created wrapper for NSHashTable and did some workaround for your compiler error.

class WeakSet<ObjectType>: SequenceType {

    var count: Int {
        return weakStorage.count
    }

    private let weakStorage = NSHashTable.weakObjectsHashTable()

    func addObject(object: ObjectType) {
        guard object is AnyObject else { fatalError("Object ((object)) should be subclass of AnyObject") }
        weakStorage.addObject(object as? AnyObject)
    }

    func removeObject(object: ObjectType) {
        guard object is AnyObject else { fatalError("Object ((object)) should be subclass of AnyObject") }
        weakStorage.removeObject(object as? AnyObject)
    }

    func removeAllObjects() {
        weakStorage.removeAllObjects()
    }

    func containsObject(object: ObjectType) -> Bool {
        guard object is AnyObject else { fatalError("Object ((object)) should be subclass of AnyObject") }
        return weakStorage.containsObject(object as? AnyObject)
    }

    func generate() -> AnyGenerator<ObjectType> {
        let enumerator = weakStorage.objectEnumerator()
        return anyGenerator {
            return enumerator.nextObject() as! ObjectType?
        }
    }
}

用法:

protocol MyDelegate : AnyObject {
    func doWork()
}

class MyClass: AnyObject, MyDelegate {
    fun doWork() {
        // Do delegated work.
    }
}

var delegates = WeakSet<MyDelegate>()
delegates.addObject(MyClass())

for delegate in delegates {
    delegate.doWork()
}

这不是最好的解决方案，因为WeakSet可以用任何类型初始化，如果这个类型不符合AnyObject协议，那么应用程序就会崩溃.但我现在看不到更好的解决方案.

It's not the best solution, because WeakSet can be initialized with any type, and if this type doesn't conform to AnyObject protocol then app will crash. But I don't see any better solution right now.

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