下面是如何使@GoZoner的伟大的答案符合哈希，所以它可以在容器对象中索引:集，字典，数组等。

private class Weak<T: AnyObject>: Hashable {
    weak var value : T!
    init (value: T) {
       self.value = value
    }

    var hashValue : Int {
       // ObjectIdentifier creates a unique hashvalue for objects.
       return ObjectIdentifier(self.value).hashValue
    }
}

// Need to override so we can conform to Equitable.
private func == <T>(lhs: Weak<T>, rhs: Weak<T>) -> Bool {
    return lhs.hashValue == rhs.hashValue
}

下面是如何使@GoZoner的伟大的答案符合哈希，所以它可以在容器对象中索引:集，字典，数组等。

private class Weak<T: AnyObject>: Hashable {
    weak var value : T!
    init (value: T) {
       self.value = value
    }

    var hashValue : Int {
       // ObjectIdentifier creates a unique hashvalue for objects.
       return ObjectIdentifier(self.value).hashValue
    }
}

// Need to override so we can conform to Equitable.
private func == <T>(lhs: Weak<T>, rhs: Weak<T>) -> Bool {
    return lhs.hashValue == rhs.hashValue
}

我有同样的想法来创建带有泛型的弱容器。 因此，我为NSHashTable创建了包装器:

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可以初始化为任何类型，如果这种类型不符合AnyObject协议，那么应用程序将崩溃，并给出详细的原因。但我现在找不到更好的解决办法。

最初的解决方案是这样定义WeakSet:

class WeakSet<ObjectType: AnyObject>: SequenceType {}

但是在这种情况下，WeakSet不能用协议初始化:

protocol MyDelegate : AnyObject {
    func doWork()
}

let weakSet = WeakSet<MyDelegate>()

目前以上代码无法编译(Swift 2.1, Xcode 7.1)。 这就是为什么我放弃符合AnyObject并使用fatalError()断言添加额外的保护。

同样的问题还有另一种解决方案……它的重点是存储对对象的弱引用，但也允许存储结构。

[我不确定它有多有用，但它确实花了一段时间来纠正语法]

class WeakWrapper : Equatable {
    var valueAny : Any?
    weak var value : AnyObject?

    init(value: Any) {
        if let valueObj = value as? AnyObject {
            self.value = valueObj
        } else {
            self.valueAny = value
        }
    }

    func recall() -> Any? {
        if let value = value {
            return value
        } else if let value = valueAny {
            return value
        }
        return nil
    }
}


func ==(lhs: WeakWrapper, rhs: WeakWrapper) -> Bool {
    return ObjectIdentifier(lhs) == ObjectIdentifier(rhs)
}



class Stuff {}
var weakArray : [WeakWrapper] = [WeakWrapper(value: Stuff()), WeakWrapper(value: CGRectZero)]

extension Array where Element : WeakWrapper  {

    mutating func removeObject(object: Element) {
        if let index = self.indexOf(object) {
            self.removeAtIndex(index)
        }
    }

    mutating func compress() {
        for obj in self {
            if obj.recall() == nil {
                self.removeObject(obj)
            }
        }
    }


}

weakArray[0].recall()
weakArray[1].recall() == nil
weakArray.compress()
weakArray.count

可以围绕Array创建包装器。或者使用这个库https://github.com/NickRybalko/WeakPointerArray let array =弱指针数组<AnyObject>() 它是类型安全的。

在很多情况下，返回一个可取消的选项会更简洁。这允许调用站点决定何时显式地销毁值(以及通过解压缩隐式地销毁值):

public protocol Cancellable {
    func cancel()
}

private struct MyValue: Identifiable {
    let id: String
    // ...
}

private class CancellationHandler: Cancellable {
    let handler: () -> ()
    init(handler: @escaping () -> ()) { self.handler = handler }
    func cancel() { handler() }
    deinit { handler() }
}

public class Container {
    private var array = [MyType]()

    public func add() -> Cancellable {
        let value = MyValue(...)
        array.append(value)
        return CancellationHandler {
            array.removeFirst(where: { $0.id == value.id })
        }
    }
}

let cancellable = container.add()

// Both cancellable.cancel() and the cancellable descoping 
// will call the `cancel` function, removing the value from array.