时间戳

首页 > 解决方案 > iOS 10 - deinit 上的 NSKeyValueObservation 崩溃

swift - iOS 10 - deinit 上的 NSKeyValueObservation 崩溃

问题描述

我NSKeyValueObservation用来观察WKWebView.

deinit它在 iOS 11 上运行良好，但在 iOS 10 上崩溃。

控制台上打印的错误日志

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'An instance 0x15209e600 of class Rakuemon.WebView was deallocated while key value observers were still registered with it. Current observation info: <NSKeyValueObservationInfo 0x170232da0> (
<NSKeyValueObservance 0x170259bf0: Observer: 0x17027d500, Key path: loading, Options: <New: NO, Old: NO, Prior: NO> Context: 0x0, Property: 0x170643ba0>
<NSKeyValueObservance 0x170643480: Observer: 0x170c72f80, Key path: estimatedProgress, Options: <New: YES, Old: NO, Prior: NO> Context: 0x0, Property: 0x170643330>
<NSKeyValueObservance 0x170642c70: Observer: 0x17086c0c0, Key path: title, Options: <New: YES, Old: NO, Prior: NO> Context: 0x0, Property: 0x1706437b0>
)'

代码

class WebView: WKWebView {

    // MARK: - Properties

    weak var delegate: WebViewDelegate?

    // MARK: - Private properties

    private var contentSizeObserver: NSKeyValueObservation?
    private var loadingObserver: NSKeyValueObservation?
    private var estimatedProgressObserver: NSKeyValueObservation?
    private var titleObserver: NSKeyValueObservation?

    // MARK: - Life cycle

    override init(frame: CGRect, configuration: WKWebViewConfiguration) {
        super.init(frame: frame, configuration: configuration)
        setupObserver()
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

// MARK: - Private functions

private extension WebView {
    func setupObserver() {
        contentSizeObserver = scrollView.observe(\.contentSize, options: [.old, .new], changeHandler: { [unowned self] _, change in
            guard let oldSize = change.oldValue, let newSize = change.newValue, oldSize != newSize else { return }
            self.delegate?.webView?(self, didChangeSizeFrom: oldSize, to: newSize)
        })

        loadingObserver = observe(\.isLoading, changeHandler: { [unowned self] _, _ in
            self.delegate?.webViewIsLoading?(self)
        })

        estimatedProgressObserver = observe(\.estimatedProgress, options: [.new], changeHandler: { [unowned self] _, change in
            guard let newValue = change.newValue else { return }
            self.delegate?.webView?(self, didChangeEstimatedProgress: newValue)
        })

        titleObserver = observe(\.title, options: [.new], changeHandler: { [unowned self] _, change in
            guard let title = change.newValue else { return }
            self.delegate?.webView?(self, didChangeTitle: title ?? "")
        })
    }
}

问题

我还发现contentSizeObserver, 它观察到的scrollView.contentSize，而不是 的属性self，并没有导致崩溃。

那么，通过 观察selfiOS 10 上的属性的正确方法是什么NSKeyValueObservation？或注销它？

标签： swiftswift4ios10key-value-observing

解决方案

更新于 2019/10/16

这似乎仍然发生在带有 Xcode 11 和 Swift 5.1 的 iOS 10.3 上，我创建了一个示例项目来使用来自SR-5752的代码对其进行测试。

到目前为止，我想出的最简单的方法是这样的：

// Environment: Xcode 11.1, Swift 5.1, iOS 10.3
deinit {
    if #available(iOS 11.0, *) {} else if let observer = observer {
        removeObserver(observer, forKeyPath: "foo")
    }
}

可以注意到我只removeObserver(_:forKeyPath)在 iOS 10 及更低版本上调用，因为正如Stacy Smith 提到的，iOS 13 上的崩溃（可以在示例项目中轻松重现）。

我也尝试了Bryan Rodríguez的建议，但没有运气。也许我错过了什么？

// Environment: Xcode 11.1, Swift 5.1, iOS 10.3
deinit {
    // Also tried only either one, no luck
    self.observer?.invalidate() 
    self.observer = nil
}

推荐阅读