A helper method that opens a native iOS flavor `CupertinoTextPicker` and `CupertinoDatePicker`

NativeCupertinoPicker.dart

void showCupertinoPicker<T>(BuildContext context,
    {bool isDatePicker = false,
    List<T> options,
    T selectedValue,
    DateTime minDate,
    DateTime lastDate,
    DateTime initialDate,
    Function(T) onChanged}) {
  showCupertinoModalPopup(
    context: context,
    builder: (context) => SizedBox(
      height: 240.0,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: <Widget>[
          Container(
            alignment: Alignment.centerRight,
            decoration: BoxDecoration(
              color: const Color.fromRGBO(249, 249, 247, 1.0),
              border: Border(
                bottom: const BorderSide(width: 0.5, color: Colors.black38),
              ),
            ),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: <Widget>[
                CupertinoButton(
                  padding: const EdgeInsets.symmetric(horizontal: 15.0),
                  child: Text(
                    'Cancel',
                    style: CupertinoTheme.of(context).textTheme.actionTextStyle.copyWith(
                          fontWeight: FontWeight.w600,
                          color: Colors.red,
                        ),
                  ),
                  onPressed: () {
                    onChanged(null);
                    Navigator.of(context).pop();
                  },
                ),
                CupertinoButton(
                  padding: const EdgeInsets.symmetric(horizontal: 15.0),
                  child: Text(
                    'Done',
                    style: CupertinoTheme.of(context).textTheme.actionTextStyle.copyWith(fontWeight: FontWeight.w600),
                  ),
                  onPressed: () => Navigator.of(context).pop(),
                ),
              ],
            ),
          ),
          Expanded(
            child: isDatePicker
                ? CupertinoDatePicker(
                    minimumDate: minDate,
                    maximumDate: lastDate,
                    initialDateTime: initialDate,
                    mode: CupertinoDatePickerMode.date,
                    onDateTimeChanged: (DateTime value) {
                      if (onChanged != null) onChanged(value as T);
                    },
                  )
                : CupertinoPicker.builder(
                    backgroundColor: Colors.white,
                    childCount: options.length,
                    itemBuilder: (BuildContext context, int index) => Center(
                      child: Text(options[index]),
                    ),
                    itemExtent: 35.0,
                    scrollController: selectedValue != null
                        ? FixedExtentScrollController(initialItem: options.indexOf(options.singleWhere((val) => val == selectedValue)))
                        : null,
                    onSelectedItemChanged: (int index) => onChanged(options[index]),
                  ),
          ),
        ],
      ),
    ),
  );
}