arrays - 如何从 Swift 中的协议(protocol)数组中删除一个元素？

Question

Swift 的协议(protocol)实现现在真的让我抓狂。我有一个数组 observers 通过自定义协议(protocol) Observing 定义，我试图从给定元素的数组中删除一个元素，但 Swift 提示 Observing 没有实现 Identifiable(我认为这实际上是我自己的另一个协议(protocol)，除非还有一个系统协议(protocol)叫它)。我只想做一个引用比较并删除实际对象。我不关心对对象执行任何类型的比较。

var observers = [Observing]()

func removeObserver( observer: Observing ) {
    for i in 0 ..< self.observers.count {
        if self.observers[i] == observer { // <='Observing' is not convertible to 'Identifiable'...?
            self.observers.removeAtIndex(i)
            break
        }
    }
}

Answer 1

== 运算符检查 Swift 中的值是否相等，并且没有默认实现。你想要的是引用相等性，你可以在 Swift 中使用 === 和 !== 来获得。

参见 the documentation了解更多详情。

Identity Operators

Because classes are reference types, it is possible for multiple constants and variables to refer to the same single instance of a class behind the scenes. (The same is not true for structures and enumerations, because they are always copied when they are assigned to a constant or variable, or passed to a function.)

It can sometimes be useful to find out if two constants or variables refer to exactly the same instance of a class. To enable this, Swift provides two identity operators:

Identical to (===) Not identical to (!==)

请注意，要使 === 运算符起作用，对象必须符合 AnyObject 协议(protocol)。您可以通过在协议(protocol)后缀“:class”来保证这一点，如下所示:

protocol SomeProtocol : class { ... }