Swift 3 图表条形图无

Question

我收到以下错误:

unexpectedly found nil while unwrapping an Optional value

我的代码如下，在我的viewDidLoad中调用了该函数:

 func setChart() {

        let months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]
        let unitsSold = [20.0, 4.0, 6.0, 3.0, 12.0, 16.0, 4.0, 18.0, 2.0, 4.0, 5.0, 4.0]


        var dataEntries: [BarChartDataEntry] = []


        for i in 0..<months.count {

            let dataEntry = BarChartDataEntry(x: Double(months[i])!, y: Double(unitsSold[i]))

            dataEntries.append(dataEntry)
        }

        let chartDataSet = BarChartDataSet(values: dataEntries, label: "Visitor count")

        let chartData = BarChartData(dataSet: chartDataSet)

        barChartView.data = chartData

    }

代码似乎在 let dataEntry 行中断。

Answer 1

您的月份数组包含月份的名称，您正试图将其转换为 Double，例如 x: Double("Jan")! ，这总是会崩溃，

所以先替换

Double(months[i])! 与 Double(i)

然后获取坐标轴标签

经过与OP的讨论，我们找到了如下解决方案，可以给x轴添加标签

yourchartView.xAxis.valueFormatter = IndexAxisValueFormatter(values:months) 
yourchartview.xAxis.granularity = 1