Невозможно удалить наблюдателя для ключевого пути «Границы», поскольку он не зарегистрирован в качестве наблюдателя

Question

Я пытаюсь добавить диаграмму в ячейку UITableView и получаю и получаю эту проблему:

2019-05-11 11:13:06.963721-0500 Prototype Settings[29076:5158720] *** Terminating app due to uncaught exception 'NSRangeException', reason: 'Cannot remove an observer <Charts.ChartDataSet 0x600003f57480> for the key path "bounds" from <Charts.ChartDataSet 0x600003f57480> because it is not registered as an observer.'
*** First throw call stack:
(
    0   CoreFoundation                      0x000000010622c6fb __exceptionPreprocess + 331
    1   libobjc.A.dylib                     0x0000000104e1aac5 objc_exception_throw + 48
    2   CoreFoundation                      0x000000010622c555 +[NSException raise:format:] + 197
    3   Foundation                          0x00000001048a05e1 -[NSObject(NSKeyValueObserverRegistration) _removeObserver:forProperty:] + 488
    4   Foundation                          0x00000001048a0a68 -[NSObject(NSKeyValueObserverRegistration) removeObserver:forKeyPath:] + 84
    5   Charts                              0x000000010438e009 $s6Charts13ChartViewBaseCfD + 105
    6   Prototype Settings                  0x0000000103d24960 $s18Prototype_Settings9ChartCellC12initDataSetsyyF + 1808
    7   Prototype Settings                  0x0000000103d28c9f $s18Prototype_Settings14SessionDetailsC9tableView_12cellForRowAtSo07UITableF4CellCSo0kF0C_10Foundation9IndexPathVtF + 1295
    8   Prototype Settings                  0x0000000103d2a44b $s18Prototype_Settings14SessionDetailsC9tableView_12cellForRowAtSo07UITableF4CellCSo0kF0C_10Foundation9IndexPathVtFTo + 155
    9   UIKitCore                           0x000000010eb8b62c -[UITableView _createPreparedCellForGlobalRow:withIndexPath:willDisplay:] + 764
    10  UIKitCore                           0x000000010eb8bb65 -[UITableView _createPreparedCellForGlobalRow:willDisplay:] + 73
    11  UIKitCore                           0x000000010eb53d20 -[UITableView _updateVisibleCellsNow:isRecursive:] + 2870
    12  UIKitCore                           0x000000010eb73e37 -[UITableView layoutSubviews] + 165
    13  UIKitCore                           0x000000010ee209c1 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 1417
    14  QuartzCore                          0x0000000106f35eae -[CALayer layoutSublayers] + 173
    15  QuartzCore                          0x0000000106f3ab88 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 396
    16  QuartzCore                          0x0000000106f46ee4 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 72
    17  QuartzCore                          0x0000000106eb63aa _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 328
    18  QuartzCore                          0x0000000106eed584 _ZN2CA11Transaction6commitEv + 608
    19  UIKitCore                           0x000000010e97a3a4 _afterCACommitHandler + 245
    20  CoreFoundation                      0x00000001061930f7 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
    21  CoreFoundation                      0x000000010618d5be __CFRunLoopDoObservers + 430
    22  CoreFoundation                      0x000000010618dc31 __CFRunLoopRun + 1505
    23  CoreFoundation                      0x000000010618d302 CFRunLoopRunSpecific + 626
    24  GraphicsServices                    0x000000010ae312fe GSEventRunModal + 65
    25  UIKitCore                           0x000000010e952ba2 UIApplicationMain + 140
    26  Prototype Settings                  0x0000000103d2bd0b main + 75
    27  libdyld.dylib                       0x0000000108568541 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

Кажется, это происходит только тогда, когда я использую эту диаграмму в ячейке UITableView.Я предполагаю, что это как-то связано с тем, как работает UITableView, но я не могу заставить его работать.

Мой код

import UIKit
import Charts

class ChartCell : UITableViewCell
{
    @IBOutlet weak var chart: LineChartView!

    var dataSet1: LineChartDataSet?
    var dataSet2: LineChartDataSet?
    var data: LineChartData?

    func initDataSets()
    {
        dataSet1 = LineChartDataSet([
            // First four must be 0 for design.
            ChartDataEntry(x: 0, y: 0),
            ChartDataEntry(x: 1, y: 0),
            ChartDataEntry(x: 2, y: 0),

            ChartDataEntry(x: 3, y: 6),
            ChartDataEntry(x: 4, y: 9),
            ChartDataEntry(x: 5, y: 5),
            ChartDataEntry(x: 6, y: 8),
            ChartDataEntry(x: 7, y: 18),
            ChartDataEntry(x: 8, y: 14),
            ChartDataEntry(x: 9, y: 12),

            // Last three must be 0 for design
            ChartDataEntry(x: 10, y: 0),
            ChartDataEntry(x: 11, y: 0)
            ])

        dataSet2 = LineChartDataSet(values: [
            // First four must be 0 for design.
            ChartDataEntry(x: 0, y: 0),
            ChartDataEntry(x: 1, y: 0),
            ChartDataEntry(x: 2, y: 0),

            ChartDataEntry(x: 3, y: 6),
            ChartDataEntry(x: 4, y: 9),
            ChartDataEntry(x: 5, y: 5),
            ChartDataEntry(x: 6, y: 8),
            ChartDataEntry(x: 7, y: 18),
            ChartDataEntry(x: 8, y: 14),
            ChartDataEntry(x: 9, y: 12),

            // Last three must be 0 for design
            ChartDataEntry(x: 10, y: 0),
            ChartDataEntry(x: 11, y: 0)
            ],
                                        label: ""
        )

        dataSet1?.drawIconsEnabled = false
        dataSet1?.drawCirclesEnabled = false
        dataSet1?.drawCircleHoleEnabled = false
        dataSet1?.drawValuesEnabled = false
        dataSet1?.lineCapType = .round
        dataSet1?.colors = [rgbToUiColor(rgb: 0xFF0000)]
        dataSet1?.highlightEnabled = false
        dataSet1?.lineWidth = 2;
        dataSet1?.mode = .horizontalBezier


        dataSet2?.drawIconsEnabled = false
        dataSet2?.drawCirclesEnabled = false
        dataSet2?.drawCircleHoleEnabled = false
        dataSet2?.drawValuesEnabled = false
        dataSet2?.lineCapType = .round
        dataSet2?.highlightEnabled = false
        dataSet2?.lineWidth = 2;
        dataSet2?.mode = .horizontalBezier
        dataSet2?.colors = [rgbToUiColor(rgb: 0x00FF00)]

        data = LineChartData(dataSets: [dataSet1!, dataSet2!])
    }

    func initializeChart()
    {
        chart.backgroundColor = UIColor(white: 1, alpha: 0)

        chart.marker = nil;
        chart.xAxis.drawAxisLineEnabled = false
        chart.xAxis.drawGridLinesEnabled = false
        chart.xAxis.drawLabelsEnabled = false
        chart.drawBordersEnabled = false;
        chart.layoutMargins = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)

        chart.leftAxis.drawAxisLineEnabled = false
        chart.leftAxis.drawGridLinesEnabled = false
        chart.leftAxis.drawLabelsEnabled = false

        chart.xAxis.enabled = false
        chart.leftAxis.enabled = false
        chart.rightAxis.enabled = false
        chart.drawBordersEnabled = false
        chart.minOffset = 0

        chart.rightAxis.drawAxisLineEnabled = false
        chart.rightAxis.drawGridLinesEnabled = false
        chart.rightAxis.drawLabelsEnabled = false
        chart.legend.enabled = false;

        chart.data = data!
        //chart.animate(xAxisDuration: 1.0, yAxisDuration: 0)
    }

    func rgbToUiColor(rgb: Int) -> UIColor {
        return UIColor(
            red: CGFloat((rgb >> 16) & 0xFF) / 255.0,
            green: CGFloat((rgb >> 8) & 0xFF) / 255.0,
            blue: CGFloat(rgb & 0xFF) / 255.0,
            alpha: 1.0
        );
    }
}

Затем я создаю ячейку со следующим:

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    . . .

    let cell = self.tableView.dequeueReusableCell(withIdentifier: "NetworkStatsGraphCell", for: indexPath) as! ChartCell
    cell.initDataSets()
    cell.initializeChart()
    return cell

    . . . 

Похоже, что это происходит в ChartViewBase.swift здесь:

deinit
{
    self.removeObserver(self, forKeyPath: "bounds")
    self.removeObserver(self, forKeyPath: "frame")
}

И этоСам ChartView, который он не может удалить из своих собственных наблюдателей, который был добавлен здесь в ChartViewBase.swift :

internal func initialize()
{
    . . .
    self.addObserver(self, forKeyPath: "bounds", options: .new, context: nil)
    self.addObserver(self, forKeyPath: "frame", options: .new, context: nil)
}