如何在@propertyWrapper 中获取父母的自我？答案

【问题标题】：How to get self of parent in @propertyWrapper?如何在@propertyWrapper 中获取父母的自我？
【发布时间】：2019-10-06 07:21:09
【问题描述】：

我想仅在事件之间经过指定间隔后处理更改的@Published someVar。如何在propertyWrapper 中获取self 的SomeClass？

private var cancellableSet: Set<AnyCancellable> = []

extension Published where Value: Equatable {
    init<S>(
        wrappedValue defaultValue: Value,
        for dueTime: S.SchedulerTimeType.Stride,
        scheduler: S,
        sink: @escaping (Value) -> () ) where S: Scheduler {
        self.init(initialValue: defaultValue)

        projectedValue
            .debounce(for: dueTime, scheduler: scheduler)
            .removeDuplicates()
            .sink(receiveValue: sink)
            .store(in: &cancellableSet)

    }
}

class SomeClass {
    @Published(
        for: 0.5,
        scheduler: RunLoop.main,
        sink: { val in
            // how to get self of SomeClass
            print(self.someVar2) //Error: Value of type '(SomeClass) -> () -> SomeClass' has no member 'someVar2'
        })
    var someVar = ""
    var someVar2 = ""
}

【问题讨论】：

标签： swift swiftui combine

【解决方案1】：

我在另一个论坛得到了以下答案

正式？你不能。

非正式的？您可以使用下划线下标 - check out this test 在 swift repo 中 29

带下划线的东西不是官方的，没有保证，可以随时删除。

我添加了我的解决方案而不使用underscored subscript

private var cancellableSet: [String: AnyCancellable] = [:]

extension Published where Value: Equatable {
    init(wrappedValue defaultValue: Value) {
        self.init(initialValue: defaultValue)
    }

    mutating func Observe<S>(
        key: String,
        for dueTime: S.SchedulerTimeType.Stride,
        scheduler: S,
        sink: @escaping (Value) -> () ) where S: Scheduler {

        print(key)
        if cancellableSet[key] == nil {
            cancellableSet[key] =
                self.projectedValue
                    .debounce(for: 0.5, scheduler: RunLoop.main)
                    .removeDuplicates()
                    .sink(receiveValue: sink)
        }
    }
}

class SomeClass {
    @Published
    var someVar = "" {
        willSet {
            _someVar.Observe(key: #function, for: 0.5, scheduler: RunLoop.main) { val in
                print(val)
            }
        }
    }
    var someVar2 = ""

    func test() {
        someVar = "a"
        someVar = "ab"
        someVar = "abc"
    }
}

SomeClass().test()

【讨论】：