ios - 当元素添加/删除到数组时得到通知

Question

我想在数组中添加/删除元素时收到通知。如果我们不是在谈论数组，例如在字符串更改时收到通知，swift 中有一个很好的解决方案:

private var privateWord: String?
var word: String? {
    get {
        return privateWord
    }
    set {
        if newValue != "" {
            notifyThatWordIsChanged()
        } else {
            notifyThatWordIsEmpty()
        }
        privateWord = newValue
    }
}

当我向数组添加/删除元素时，我们能否获得类似的结果？

Answer 1

您可以创建类似类/结构的代理，它们将具有与数组相同的接口(interface)，将在场景下存储标准数组并代表存储数组。这是一个小例子:

struct ArrayProxy<T> {
    var array: [T] = []

    mutating func append(newElement: T) {
        self.array.append(newElement)
        print("Element added")
    }

    mutating func removeAtIndex(index: Int) {
        print("Removed object \(self.array[index]) at index \(index)")
        self.array.removeAtIndex(index)
    }

    subscript(index: Int) -> T {
        set {
            print("Set object from \(self.array[index]) to \(newValue) at index \(index)")
            self.array[index] = newValue
        }
        get {
            return self.array[index]
        }
    }
}

var a = ArrayProxy<Int>()
a.append(1)