如何在Swift中声明一个弱引用数组? [英] How do I declare an array of weak references in Swift?

问题描述

我想在Swift中存储一系列弱引用.数组本身不应该是一个弱引用-它的元素应该是.我认为可可NSPointerArray为此提供了非类型安全的版本.

I'd like to store an array of weak references in Swift. The array itself should not be a weak reference - its elements should be. I think Cocoa NSPointerArray offers a non-typesafe version of this.

推荐答案

创建通用包装器为:

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

将此类的实例添加到您的数组中.

Add instances of this class to your array.

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

定义Weak时，可以使用struct或class.

此外，为了帮助获取数组内容，您可以按照以下方式进行操作:

Also, to help with reaping array contents, you could do something along the lines of:

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

上面的AnyObject的使用应替换为T-但我不认为当前的Swift语言允许这样定义扩展名.

The use of AnyObject above should be replaced with T - but I don't think the current Swift language allows an extension defined as such.

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