dataLabelMapper property Null safety

ChartIndexedValueMapper<String>? dataLabelMapper
final

Field in the data source, which is considered as text for the data points.

Defaults to null

Widget build(BuildContext context) {
   return Container(
       child: SfCartesianChart(
           series: <BarSeries<SalesData, num>>[
               BarSeries<SalesData, num>(
                dataSource: <SalesData>[
                   SalesData(DateTime(2005, 0, 1), 'India', 16),
                   SalesData(DateTime(2006, 0, 1), 'China', 12),
                   SalesData(DateTime(2007, 0, 1), 'USA',18),
                ],
               dataLabelSettings: DataLabelSettings(isVisible:true),
               dataLabelMapper: (SalesData data, _) => data.category,
             ),
            ],
       ));
}
class SalesData {
  SalesData(this.year, this.category, this.sales1);
  final DateTime year;
  final String category;
  final int sales1;
}

Implementation

@override
final ChartIndexedValueMapper<String>? dataLabelMapper;