不支持使用符合协议AnyObject的具体类型 [英] Using as a concrete type conforming to protocol AnyObject is not supported

问题描述

我正在使用Swift 2并使用WeakContainer作为存储一组弱对象的方法，就像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中声明

Then in my ViewController, I declare

public var delegates = [WeakContainer<MyDelegate>]

但这是错误的

不支持将MyDelegate用作符合协议AnyObject的具体类型

Using MyDelegate as a concrete type conforming to protocol AnyObject is not supported

我看到错误是WeakContainer具有声明为weak的value成员，因此T应该是对象.但是我也将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

我有相同的想法来创建具有泛型的弱容器.
结果，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()
}

这不是最佳解决方案，因为WeakSet可以使用任何类型进行初始化，并且如果此类型不符合AnyObject协议，则应用程序将崩溃.但是我现在没有更好的解决方案.

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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