DelayOutputPublisher

一个 Combine Publisher，通过在输出之间插入延迟来限制吞吐量。

与 throttle(for:scheduler:latest:) 和 debounce(for:scheduler:options:) 不同，delayOutput(for:tolerance:scheduler:options:) 不会丢弃输出元素。

第一个输出元素将被立即调度。后续元素可能会被指定的间隔延迟。

用法

使用 Publisher 的 delayOutput(for:tolerance:scheduler:options:) 方法来获取一个 DelayOutputPublisher。

第一个输出将被立即调度，任何后续输出将在上次输出传递完成后（在 subscriber.receive() 返回后）被调度。

let df = DateFormatter()
df.dateStyle = .none
df.timeStyle = .medium

print("Start at \(df.string(from: Date()))")

let cancellable = (0..<4).publisher
    .delayOutput(for: .seconds(1), scheduler: RunLoop.main)
    .sink(
        receiveCompletion: { print("completed \($0)") },
        receiveValue: { value in
            print("Received \(value) after \(df.string(from: Date()))")
        })

输出

Start at 18:22:21
Received 0 after 18:22:21
Received 1 after 18:22:22
Received 2 after 18:22:23
Received 3 after 18:22:24
completed finished

一个 SwiftUI 示例，展示了如何限制

class SlowCounter: ObservableObject {
    private let subject: PassthroughSubject<Int, Never>
    let delayed: DelayOutputPublisher<PassthroughSubject<Int, Never>, RunLoop>

    init() {
        subject = PassthroughSubject<Int, Never>()
        delayed = subject
            .delayOutput(for: .seconds(1), scheduler: RunLoop.main)
    }

    private(set) var count = 0
    func addOne() {
        count += 1
        subject.send(count)
    }
}

struct MyView: View {
    @ObservedObject var counter = SlowCounter()
    @State var count = 0

    var body: some View {
        Text("Hello \(count)")
            .onReceive(counter.delayed) { count = $0 }

        Button("Increase!") {
            counter.addOne()
        }
    }
}

演示

安装

Package.swift

编辑 Package.swift 文件。将 DelayOutputPublisher 添加为依赖项

let package = Package(
    name: " ... ",
    products: [ ... ],
    dependencies: [
        .package(url: "https://github.com/berikv/DelayOutputPublisher.git", from: "1.0.0") // here
    ],
    targets: [
        .target(
            name: " ... ",
            dependencies: [
                "DelayOutputPublisher" // and here
            ]),
    ]
)

对于 .xcodeproj 项目

打开菜单 File > Add Packages...
搜索 "https://github.com/berikv/DelayOutputPublisher.git" 并点击 Add Package。
打开你的项目文件，在 "Targets" 中选择你的目标。
打开 Dependencies
点击 + 号
添加 DelayOutputPublisher