ios - 使用 RXSwift 观察 contentSize 时检测到重入异常

Question

我对 RXSwift 的 TableView 进行了以下设置:

override func viewDidLoad() {
    super.viewDidLoad()

    // Constraints setup etc
    
    items
        .subscribeOn(MainScheduler.instance)
        .bind(to: tableView.rx.items(cellType: SomeCell.self)) { [weak self] row, item, cell in
            // Code
        }
        .disposed(by: bag)

    // Observe the contentSize of tableView to update PanModal's height.
    tableView.rx.observe(CGRect.self, "contentSize")
        .subscribeOn(MainScheduler.instance)
        .subscribe(onNext: { [weak self] _ in
            // Code
        })
        .disposed(by: bag)
}

似乎是因为我使用 RXSwift 订阅了 contentSize 我现在收到以下错误:

⚠️ Reentrancy anomaly was detected. Debugging: To debug this issue you can set a breakpoint in /Users/kekearif/Documents/Snapask/ios-app/Pods/RxSwift/RxSwift/Rx.swift:96 and observe the call stack. Problem: This behavior is breaking the observable sequence grammar. next (error | completed)? This behavior breaks the grammar because there is overlapping between sequence events. Observable sequence is trying to send an event before sending of previous event has finished. Interpretation: This could mean that there is some kind of unexpected cyclic dependency in your code, or that the system is not behaving in the expected way. Remedy: If this is the expected behavior this message can be suppressed by adding .observeOn(MainScheduler.asyncInstance) or by enqueuing sequence events in some other way.

有没有人见过这个？任何想法可能导致此错误的原因是什么？我尝试按照它的建议添加 .observeOn(MainScheduler.asyncInstance)，当我显示 View Controller 时，UI 就锁定了。

如有任何关于如何解决此问题的建议，我们将不胜感激!

Answer 1

不是因为您订阅了contentSize，请注意您发布的代码不会导致异常；这是因为您在订阅(或绑定(bind))中所做的事情导致了问题的发生。

如您收到的警告中所述，“可观察序列正在尝试在上一个事件发送完成之前发送一个事件。”这通常是由程序员在绑定(bind)到主题的订阅内的主题上发送 onNext 事件引起的。在这种情况下，您可能会从订阅内部更改 TableView 的 contentSize。解决方案是不要这样做。

详细解释您认为需要这样做的原因，也许我可以向您展示更好的方法。