如何在“纯”Swift（w / o @objc）中做出弱协议参考 [英] How can I make a weak protocol reference in 'pure' Swift (w/o @objc)

问题描述

weak 引用在Swift中似乎不起作用，除非协议被声明为 @objc ，我不想在一个纯粹的Swift应用程序。

weak references don't seem to work in Swift unless a protocol is declared as @objc, which I don't want in a pure Swift app.

这段代码给出一个编译错误（ weak 不能应用于非类型 MyClassDelegate ）：

This code gives a compile error (weak cannot be applied to non-class type MyClassDelegate):

class MyClass {
  weak var delegate: MyClassDelegate?
}

protocol MyClassDelegate {
}

我需要在协议前加上 @objc ，然后才可以使用。

I need to prefix the protocol with @objc, then it works.

问题：什么是纯快捷方式来完成 weak 委托？

Question: What is the 'pure' Swift way to accomplish a weak delegate?

推荐答案

您需要将协议的类型声明为 class 。

You need to declare the type of the protocol as class.

protocol ProtocolNameDelegate: class {
    // Protocol stuff goes here
}

class SomeClass {
    weak var delegate: ProtocolNameDelegate?
}

我的理解是使用 class ，你保证这个协议只能用于类，没有其他的东西像枚举或结构。

My understanding is that using class, you guarantee that this protocol will be used only on classes and no other stuff like enums or structs.

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