Can't cancel executing operations in OperationQueue swift

Im doing some lengthy calculations to create chart data on a background thread

i was originally use GCD, but every time a user filters the chart data by hitting a button, the chart data needs to be recalculated, if the user clicks the chart data filtering buttons very quickly (power user) then the chart loops through each drawing as each GCD dispatch async finishes

I realize that I can't cancel threads with GCD so I've moved to trying to implement an OperationQueue

I call cancelAllOperations() before adding a new operation to the queue

The operations on the queue act funky, sometimes it seems like they are cancelled, some times it seems like the one that finished is not the most recent one put on the queue.

I am also having trouble cancelling a executing operation as the operation's .isCancelled property is never true when i check for it in the operations completion block

What i really want is if the chart data calculation is currently happening in a background thread, and a user clicks another filter button and kicks off another chart calculation on a background thread, the previous chart background thread calculation is terminated and "replaced" with the most recently added operation

is this possible? here is some code:

func setHistoricalChart() -> Void {
    self.lineChartView.clear()
    self.lineChartView.noDataText = "Calculating Historical Totals, Please Wait..."

    self.historicalOperationsQueue.qualityOfService = .utility
    self.historicalOperationsQueue.maxConcurrentOperationCount = 1
    self.historicalOperationsQueue.name = "historical operations queue"

    let historicalOperation = Operation()
    historicalOperation.completionBlock = { [weak self] in
        //dictionary of feeds, array of data for each feed
        var valuesByFeed = [String:[String]?]()
        var dates = [String:[String]?]()
        var chartDataSets = [IChartDataSet]()

        //get data and values from DataMOs in the activeFeeds
        if (self?.activeFeeds.count)! > 0 {
            //check if operation is cancelled
            if historicalOperation.isCancelled {
                return
            }
            for (key, feed) in (self?.activeFeeds)! {
                dates[key] = feed?.datas?.flatMap({ Utils.formatUTCDateString(utcDateString: ($0 as! DataMO).utcDateString) })
                valuesByFeed[key] = feed?.datas?
                    .sorted(by: { (($0 as! DataMO).utcDateString)! < (($1 as! DataMO).utcDateString)! })
                    .flatMap({ ($0 as! DataMO).value })
            }

            //Create Chart Data
            for (key, valuesArray) in valuesByFeed {
                var dataEntries = [ChartDataEntry]()
                for (index, value) in (valuesArray?.enumerated())! {
                    let dataEntry = ChartDataEntry(x: Double(index), y: Double(value)!)
                    dataEntries.append(dataEntry)
                }
                let singleChartDataSet = LineChartDataSet(values: dataEntries, label: key)
                singleChartDataSet.drawCirclesEnabled = false
                switch key {
                case "Solar":
                    singleChartDataSet.setColors(UIColor(red: 230/255, green: 168/255, blue: 46/255, alpha: 1))
                    singleChartDataSet.drawFilledEnabled = true
                    singleChartDataSet.fillColor = UIColor(red: 230/255, green: 168/255, blue: 46/255, alpha: 0.8)
                    break
                case "Wind":
                    singleChartDataSet.setColors(UIColor(red: 73/255, green: 144/255, blue: 226/255, alpha: 1))
                    singleChartDataSet.drawFilledEnabled = true
                    singleChartDataSet.fillColor = UIColor(red: 73/255, green: 144/255, blue: 226/255, alpha: 0.8)
                    break
                case "Battery":
                    singleChartDataSet.setColors(UIColor(red: 126/255, green: 211/255, blue: 33/255, alpha: 1))
                    singleChartDataSet.drawFilledEnabled = true
                    singleChartDataSet.fillColor = UIColor(red: 126/255, green: 211/255, blue: 33/255, alpha: 0.8)
                    break
                case "Gen":
                    singleChartDataSet.setColors(UIColor(red: 208/255, green: 1/255, blue: 27/255, alpha: 1))
                    singleChartDataSet.drawFilledEnabled = true
                    singleChartDataSet.fillColor = UIColor(red: 208/255, green: 1/255, blue: 27/255, alpha: 0.8)
                    break
                case "Demand":
                    singleChartDataSet.setColors(UIColor(red: 128/255, green: 133/255, blue: 233/255, alpha: 1))
                    singleChartDataSet.drawFilledEnabled = true
                    singleChartDataSet.fillColor = UIColor(red: 128/255, green: 133/255, blue: 233/255, alpha: 0.8)
                    break
                case "Prod":
                    singleChartDataSet.setColors(UIColor(red: 241/255, green: 92/255, blue: 128/255, alpha: 1))
                    singleChartDataSet.drawFilledEnabled = true
                    singleChartDataSet.fillColor = UIColor(red: 241/255, green: 92/255, blue: 128/255, alpha: 0.8)
                    break
                default:
                    break
                }
                chartDataSets.append(singleChartDataSet)
            }
        }

        //check if operation is cancelled
        if historicalOperation.isCancelled {
            return
        }

        //set chart data
        let chartData = LineChartData(dataSets: chartDataSets)

        //update UI on MainThread
        OperationQueue.main.addOperation({
            if (self?.activeFeeds.count)! > 0 {
                self?.lineChartView.data = chartData
            } else {
                self?.lineChartView.clear()
                self?.lineChartView.noDataText = "No Feeds To Show"
            }
        })
    }
    historicalOperationsQueue.cancelAllOperations()
    historicalOperationsQueue.addOperation(historicalOperation)
}