main.dart

void main() {
  final grid = Grid<Employee>(
    columns: [
      Column<Employee, String>(
        valueResolver: (employee) => employee.name,
        valueFormatter: (value) => value.toUpperCase(),
      ),
      Column<Employee, double>(
        valueResolver: (employee) => employee.salary,
        valueFormatter: (value) => value.toStringAsFixed(2),
      ),
    ],
    items: [
      Employee('John', 100.24),
      Employee('Mary', 130.15),
    ],
  );

  grid.render();
}

typedef CellValueFormatter<VALUE> = String Function(VALUE);
typedef CellValueResolver<ITEM, VALUE> = VALUE Function(ITEM);

class Employee {
  Employee(this.name, this.salary);

  final String name;
  final double salary;
}

class Grid<ITEM> {
  final List<Column<ITEM, Object>> columns;
  final List<ITEM> items;

  Grid({
    required this.columns,
    required this.items,
  });

  void render() {
    for (final item in items) {
      final result = StringBuffer();

      for (final column in columns) {
        final value = column.valueResolver(item);
        final formattedValue = column.valueFormatter(value);
        result.write(formattedValue);
        result.write(';');
      }

      print(result.toString());
    }
  }
}

class Column<ITEM, VALUE> {
  Column({
    required this.valueResolver,
    required this.valueFormatter,
  });

  final CellValueResolver<ITEM, VALUE> valueResolver;
  final CellValueFormatter<VALUE> valueFormatter;
}