在 [SomeProtocol] 类型的数组中查找对象的索引

问题描述

我有一个名为subscribers 的数组，用于存储符合JABPanelChangeSubscriber 协议的对象.协议声明为

I have an array called subscribers that stores objects which conform to the protocol JABPanelChangeSubscriber. The protocol is declared as

public protocol JABPanelChangeSubscriber {

}

我的数组被声明为:

var subscribers = [JABPanelChangeSubscriber]()

现在我需要实现一种方法来将订阅者添加到列表中，但首先必须检查该订阅者之前是否尚未添加过.

Now I need to implement a method to add a subscriber to the list, but it first has to check that that subscriber has not already been added before.

public func addSubscriber(subscriber: JABPanelChangeSubscriber) {
    if subscribers.find(subscriber) == nil { // This ensures that the subscriber has never been added before
        subscribers.append(subscriber)
    }
}

不幸的是，JABPanelChangeSubscriber 不是 Equatable，我不知道如何使它成为 Equatable，所以 find 方法给了我一个错误.任何人都可以帮助我解决问题或提出不同方法的建议吗?

Unfortunately, JABPanelChangeSubscriber is not Equatable, and I can't figure out how to make it Equatable, so the find method is giving me an error. Can anyone help me out with a fix or with a suggestion for a different approach?

谢谢

推荐答案

假设实现你的协议的所有类型都是引用类型(类)，你可以将协议声明为类协议"

Assuming that all types implementing your protocol are reference types(classes), you can declare the protocol as a "class protocol"

public protocol JABPanelChangeSubscriber : class {

}

并使用恒等运算符 === 来检查数组是否已经包含指向与给定参数相同的实例的元素:

and use the identity operator === to check if the array alreadycontains an element pointing to the same instance as the given argument:

public func addSubscriber(subscriber: JABPanelChangeSubscriber) {
    if !contains(subscribers, { $0 === subscriber } ) {
        subscribers.append(subscriber)
    }
}

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