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。

创建一个通用包装器，如下:

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

将该类的实例添加到数组中。

class Stuff {}
var weakly : [Weak<Stuff>] = [Weak(value: Stuff()), Weak(value: Stuff())]

定义Weak时，可以使用struct或class。

同样，为了帮助获取数组内容，你可以做一些如下的事情:

extension Array where Element:Weak<AnyObject> {
  mutating func reap () {
    self = self.filter { nil != $0.value }
  }
}

上面使用的AnyObject应该替换为T -但我不认为当前的Swift语言允许这样定义扩展。

函数式样式包装器呢?

class Class1 {}

func captureWeakly<T> (_ target:T) -> (() -> T?) where T: AnyObject {
    return { [weak target] in
        return target
    }
}

let obj1 = Class1()
let obj2 = Class1()
let obj3 = Class1()
let captured1 = captureWeakly(obj1)
let captured2 = captureWeakly(obj2)
let captured3 = captureWeakly(obj3)

只需调用返回的闭包来检查目标是否仍然存在。

let isAlive = captured1() != nil
let theValue = captured1()!

你可以把闭包存储到一个数组中。

let array1 = Array<() -> (Class1?)>([captured1, captured2, captured3])

您可以通过映射调用闭包来检索弱捕获的值。

let values = Array(array1.map({ $0() }))

实际上，你不需要一个函数来创建闭包。直接捕获一个对象。

let captured3 = { [weak obj3] in return obj3 }

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

可以通过创建包装器对象来保存弱指针来实现这一点。

struct WeakThing<T: AnyObject> {
  weak var value: T?
  init (value: T) {
    self.value = value
  }
}

然后在数组中使用这些

var weakThings = WeakThing<Foo>[]()

细节

Swift 5.1, Xcode 11.3.1

解决方案

struct WeakObject<Object: AnyObject> { weak var object: Object? }

选项1

@propertyWrapper
struct WeakElements<Collect, Element> where Collect: RangeReplaceableCollection, Collect.Element == Optional<Element>, Element: AnyObject {
    private var weakObjects = [WeakObject<Element>]()

    init(wrappedValue value: Collect) { save(collection: value) }

    private mutating func save(collection: Collect) {
        weakObjects = collection.map { WeakObject(object: $0) }
    }

    var wrappedValue: Collect {
        get { Collect(weakObjects.map { $0.object }) }
        set (newValues) { save(collection: newValues) }
    }
}

选项1用法

class Class1 { // or struct
    @WeakElements var weakObjectsArray = [UIView?]() // Use like regular array. With any objects

    func test() {
        weakObjectsArray.append(UIView())
        weakObjectsArray.forEach { print($0) }
    }
}

选项2

struct WeakObjectsArray<Object> where Object: AnyObject {
    private var weakObjects = [WeakObject<Object>]()
}

extension WeakObjectsArray {
    typealias SubSequence = WeakObjectsArray<Object>
    typealias Element = Optional<Object>
    typealias Index = Int
    var startIndex: Index { weakObjects.startIndex }
    var endIndex: Index { weakObjects.endIndex }
    func index(after i: Index) -> Index { weakObjects.index(after: i) }
    subscript(position: Index) -> Element {
        get { weakObjects[position].object }
        set (newValue) { weakObjects[position] = WeakObject(object: newValue) }
    }
    var count: Int { return weakObjects.count }
    var isEmpty: Bool { return weakObjects.isEmpty }
}

extension WeakObjectsArray: RangeReplaceableCollection {
    mutating func replaceSubrange<C : Collection>( _ subrange: Range<Index>, with newElements: C) where Element == C.Element {
        weakObjects.replaceSubrange(subrange, with: newElements.map { WeakObject(object: $0) })
    }
}

选项2使用

class Class2 { // or struct
    var weakObjectsArray = WeakObjectsArray<UIView>() // Use like regular array. With any objects

    func test() {
        weakObjectsArray.append(UIView())
        weakObjectsArray.forEach { print($0) }
    }
}

完整的样品

不要忘记粘贴解决方案代码

import UIKit

class ViewController: UIViewController {

    @WeakElements var weakObjectsArray = [UIView?]()
    //var weakObjectsArray = WeakObjectsArray<UIView>()

    override func viewDidLoad() {
        super.viewDidLoad()
        addSubviews()
    }

    private func printArray(title: String) {
        DispatchQueue.main.async {
            print("=============================\n\(title)\ncount: \(self.weakObjectsArray.count)")
            self.weakObjectsArray.enumerated().forEach { print("\($0) \(String(describing: $1))") }
        }
    }
}

extension ViewController {

    private func createRandomRectangleAndAdd(to parentView: UIView) -> UIView {
        let view = UIView(frame: CGRect(x: Int.random(in: 0...200),
                                        y: Int.random(in: 60...200),
                                        width: Int.random(in: 0...200),
                                        height: Int.random(in: 0...200)))
        let color = UIColor(red: CGFloat.random(in: 0...255)/255,
                            green: CGFloat.random(in: 0...255)/255,
                            blue: CGFloat.random(in: 0...255)/255,
                            alpha: 1)
        view.backgroundColor = color
        parentView.addSubview(view)
        return view
    }

    private func addSubviews() {
        (0...1).forEach { _ in addView() }
        addButtons()
    }

    private func createButton(title: String, frame: CGRect, action: Selector) -> UIButton {
        let button = UIButton(frame: frame)
        button.setTitle(title, for: .normal)
        button.addTarget(self, action: action, for: .touchUpInside)
        button.setTitleColor(.blue, for: .normal)
        return button
    }

    private func addButtons() {
        view.addSubview(createButton(title: "Add",
                                     frame: CGRect(x: 10, y: 20, width: 40, height: 40),
                                     action: #selector(addView)))

        view.addSubview(createButton(title: "Delete",
                                     frame: CGRect(x: 60, y: 20, width: 60, height: 40),
                                     action: #selector(deleteView)))

        view.addSubview(createButton(title: "Remove nils",
                                     frame: CGRect(x: 120, y: 20, width: 100, height: 40),
                                     action: #selector(removeNils)))
    }

    @objc func deleteView() {
        view.subviews.first { view -> Bool in return !(view is UIButton) }?
            .removeFromSuperview()

        printArray(title: "First view deleted")
    }

    @objc func addView() {
        weakObjectsArray.append(createRandomRectangleAndAdd(to: view))
        printArray(title: "View addded")
    }

    @objc func removeNils() {
        weakObjectsArray = weakObjectsArray.filter { $0 != nil }
        printArray(title: "Remove all nil elements in weakArray")
    }
}