[英]View refreshing not triggered when ObservableObject is inherited in SwiftUI
[英]ObservedObject inside ObservableObject not refreshing View
我试图在执行异步请求时显示活动指示器。 我所做的是创建一个 ActivityTracker object 来跟踪发布者的生命周期。 此 ActivityTracker 是一个 ObservableObject 并将存储在视图 model 中,该视图也是一个 ObservableObject。
似乎这种设置并没有刷新视图。 这是我的代码:
struct ContentView: View {
@ObservedObject var viewModel = ContentViewModel()
var body: some View {
VStack(spacing: 16) {
Text("Counter: \(viewModel.tracker.count)\nPerforming: \(viewModel.tracker.isPerformingActivity ? "true" : "false")")
Button(action: {
_ = request().trackActivity(self.viewModel.tracker).sink { }
}) {
Text("Request")
}
}
}
}
class ContentViewModel: ObservableObject {
@Published var tracker = Publishers.ActivityTracker()
}
private func request() -> AnyPublisher<Void, Never> {
return Just(()).delay(for: 2.0, scheduler: RunLoop.main)
.eraseToAnyPublisher()
}
extension Publishers {
final class ActivityTracker: ObservableObject {
// MARK: Properties
@Published var count: Int = 0
var isPerformingActivity: Bool {
return count > 0
}
private var cancellables: [AnyCancellable] = []
private let counterSubject = CurrentValueSubject<Int, Never>(0)
private let lock: NSRecursiveLock = .init()
init() {
counterSubject.removeDuplicates()
.receive(on: RunLoop.main)
.print()
.sink { [weak self] counter in
self?.count = counter
}
.store(in: &cancellables)
}
// MARK: Private methods
fileprivate func trackActivity<Value, Error: Swift.Error>(
ofPublisher publisher: AnyPublisher<Value, Error>
) {
publisher
.receive(on: RunLoop.main)
.handleEvents(
receiveSubscription: { _ in self.increment() },
receiveOutput: nil,
receiveCompletion: { _ in self.decrement() },
receiveCancel: { self.decrement() },
receiveRequest: nil
)
.print()
.sink(receiveCompletion: { _ in }, receiveValue: { _ in })
.store(in: &cancellables)
}
private func increment() {
lock.lock()
defer { lock.unlock() }
counterSubject.value += 1
}
private func decrement() {
lock.lock()
defer { lock.unlock() }
counterSubject.value -= 1
}
}
}
extension AnyPublisher {
func trackActivity(_ activityTracker: Publishers.ActivityTracker) -> AnyPublisher {
activityTracker.trackActivity(ofPublisher: self)
return self
}
}
我还尝试将我的 ActivityTracker 声明为@Published
但结果相同,我的文本没有更新。 请注意,将活动跟踪器直接存储在视图中会起作用,但这不是我想要的。
我在这里错过了什么吗?
尚不支持嵌套的 ObservableObjects。 当您要使用这些嵌套对象时,您需要在数据发生更改时自行通知对象。 我希望以下代码可以帮助您解决问题。
首先使用: import Combine
然后声明您的 model 和子模型,它们都需要使用@ObservableObject
属性才能工作。 (不要忘记@Published
属性)
我制作了一个名为Model的父 model 和两个子模型Submodel1 和 Submodel2 。 当您在更改数据时使用父 model 时: model.submodel1.count
,您需要使用通知程序以让视图自行更新。
AnyCancellables通知父 model 本身,在这种情况下,视图将自动更新。
复制代码并自己使用,然后在使用时尝试重新制作代码。 希望这有帮助,祝你好运!
class Submodel1: ObservableObject {
@Published var count = 0
}
class Submodel2: ObservableObject {
@Published var count = 0
}
class Model: ObservableObject {
@Published var submodel1 = Submodel1()
@Published var submodel2 = Submodel2()
var anyCancellable: AnyCancellable? = nil
var anyCancellable2: AnyCancellable? = nil
init() {
anyCancellable = submodel1.objectWillChange.sink { [weak self] (_) in
self?.objectWillChange.send()
}
anyCancellable2 = submodel2.objectWillChange.sink { [weak self] (_) in
self?.objectWillChange.send()
}
}
}
当你想使用这个Model时,就像正常使用 ObservedObjects 一样使用它。
struct Example: View {
@ObservedObject var obj: Model
var body: some View {
Button(action: {
self.obj.submodel1.count = 123
// If you've build a complex layout and it still won't work, you can always notify the modal by the following line of code:
// self.obj.objectWillChange.send()
}) {
Text("Change me")
}
}
如果你有一堆东西,你可以这样做:
import Foundation
import Combine
class Submodel1: ObservableObject {
@Published var count = 0
}
class Submodel2: ObservableObject {
var anyCancellable: [AnyCancellable] = []
@Published var submodels: [Submodel1] = []
init() {
submodels.forEach({ submodel in
anyCancellable.append(submodel.objectWillChange.sink{ [weak self] (_) in
self?.objectWillChange.send()
})
})
}
}
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