合并和NotificationCenter:通知不起作用

Question

我写了一个非常简单的应用来测试Combine和NotificationCenter：

extension Notification.Name {
    static let Test = Notification.Name(rawValue: "Test")
}

// SOLUTION 1
NotificationCenter.default
            .publisher(for: .Test)
            .sink(receiveCompletion: { _ in
                print("SOLUTION 1: COMPLETION")
            }, receiveValue: { _ in
                print("SOLUTION 1: VALUE")
            })

// SOLUTION 2
    NotificationCenter.Publisher(center: .default, name: .Test)
        .sink(receiveCompletion: { _ in
            print("SOLUTION 2: COMPLETION")
        }, receiveValue: { _ in
            print("SOLUTION 2: VALUE")
        })

// SOLUTION 3
NotificationCenter.default.addObserver(self, selector: #selector(doSomething), name: .Test, object: nil)

@objc
func doSomething() {
        print("SOLUTION 3: VALUE")
}

// RAISE NOTIFICATION

NotificationCenter.default.post(name: .Test, object: nil)NotificationCenter.default.post(name: .Test, object: nil)

使用Combine不能捕获通知。唯一有效的解决方案是第三种方案，即老式方案。奇怪的是，如果我在Playground中运行相同的代码，它就能工作！

该项目的部署目标是iOS 13。我已经在物理设备和模拟器上执行了该应用程序。我还安装了iOS 13.2.2模拟器。

有什么建议吗？

Answer 1

不要忘记将您的可取消实例存储在一个集合或变量中。示例(使用Set)：

private var cancellableBag = Set<AnyCancellable>()

NotificationCenter.default
    .publisher(for: .Test)
    .sink(receiveCompletion: { _ in
        print("SOLUTION 1: COMPLETION")
    }, receiveValue: { _ in
        print("SOLUTION 1: VALUE")
    })
    .store(in: &cancellableBag)

或者使用变量：

private let cancellable: AnyCancellable?

cancellable = NotificationCenter.default
    .publisher(for: .Test)
    .sink(receiveCompletion: { _ in
        print("SOLUTION 1: COMPLETION")
    }, receiveValue: { _ in
        print("SOLUTION 1: VALUE")
    })