class IoniaTip { const IoniaTip({this.originalAmount, this.percentage}); final double originalAmount; final double percentage; double get additionalAmount => double.parse((originalAmount * percentage / 100).toStringAsFixed(2)); static const tipList = [ IoniaTip(originalAmount: 0, percentage: 0), IoniaTip(originalAmount: 10, percentage: 10), IoniaTip(originalAmount: 20, percentage: 20) ]; }