format property Null safety

String? format

Text format of the interactive tooltip.

By default, axis value will be displayed in the tooltip, and it can be customized by adding desired text as prefix or suffix.

Widget build(BuildContext context) {
   return Container(
       child: SfCartesianChart(
          trackballBehavior: TrackballBehavior(enable: true,
          tooltipSettings: InteractiveTooltip(
            format:'point.x %')),


final String? format;