Crash when using BarChartDataSet with BarChartData

[spencerkohan]

• I've read, understood, and done my best to follow the *CONTRIBUTING guidelines.

What did you do?

I'm attempting to implement a simple bar chart. I've instantiated the data like so:

    let chartView = BarChartView(frame: chartContainer.bounds)
    let data = (0..<10).map { (i) -> BarChartDataEntry in
        return BarChartDataEntry(x: Double(i), y: Double.random(in: 1..<10))
    }
    
    let dataset: BarChartDataSet = BarChartDataSet(data)
    let chartData: BarChartData = BarChartData(dataSets: [dataset])
    
    guard (chartData.dataSets.first as? IBarChartDataSet) != nil else {
        print("WTF???")
        return
    }

    chartView.data = chartData

What did you expect to happen?

I expect that there is not a crash when the chart is loaded.

What happened instead?

There is a crash inside BarChartRenderer-initBuffers on line 76:

let set = barData.dataSets[i] as! IBarChartDataSet

For some reason, the dataset no longer conforms to IBarChartDataSet when it reaches this point.

I have also checked immediately after initializing the BarChartData, and it's already broken there:

    let dataset: BarChartDataSet = BarChartDataSet(data)
    let chartData: BarChartData = BarChartData(dataSets: [dataset])

    // this guard passes: dataset is an IBarChartDataSet
    guard (dataset as? IBarChartDataSet) != nil else { 
        return
    }

    // this one fails.  shouldn't it be the same?
    guard (chartData.dataSets.first as? IBarChartDataSet) != nil else {
        print("WTF???")
        return
    }

Charts Environment

Charts version/Branch/Commit Number: 3.0/master/e850593
Xcode version: 10.2.1
Swift version: 5.0
Platform(s) running Charts: iOS
macOS version running Xcode: 10.14.5

[glisom]

Any work around on this??

[liuxuan30]

I suggest you take a look at ChartsDemo and try reproduce with it