formatEditUpdate method

  1. @override
TextEditingValue formatEditUpdate(
  1. TextEditingValue oldValue,
  2. TextEditingValue newValue
)
override

Called when text is being typed or cut/copy/pasted in the EditableText.

You can override the resulting text based on the previous text value and the incoming new text value.

When formatters are chained, oldValue reflects the initial value of TextEditingValue at the beginning of the chain.

Implementation

@override
TextEditingValue formatEditUpdate(
  TextEditingValue oldValue,
  TextEditingValue newValue,
) {
  final text = newValue.text;

  /// Allow deleting
  if (text.length < oldValue.text.length) {
    return newValue;
  }

  /// Remove any non-digit characters except /
  String cleaned = text.replaceAll(RegExp(r'[^\d/]'), '');

  // Don't allow consecutive slashes
  cleaned = cleaned.replaceAll(RegExp(r'/+'), '/');

  // Split by / to check each part
  List<String> parts = cleaned.split('/');

  // Validate and limit each part
  String formatted = '';

  if (parts.isNotEmpty) {
    // Day - max 2 digits, max value 31
    String day = parts[0];
    if (day.length > 2) {
      day = day.substring(0, 2);
    }
    if (day.isNotEmpty && int.tryParse(day) != null) {
      int dayNum = int.parse(day);
      if (dayNum > 31) {
        day = '31';
      }
    }
    formatted = day;

    // Auto-add slash after 2 digits for day
    if (day.length == 2 && text.endsWith(day) && !text.contains('/')) {
      formatted += '/';
    }
  }

  if (parts.length > 1) {
    // Month - max 2 digits, max value 13 (for Ethiopian calendar)
    String month = parts[1];
    if (month.length > 2) {
      month = month.substring(0, 2);
    }
    if (month.isNotEmpty && int.tryParse(month) != null) {
      int monthNum = int.parse(month);
      if (monthNum > 13) {
        month = '13';
      }
    }
    formatted += '/$month';

    // Auto-add slash after 2 digits for month
    if (month.length == 2 && text.endsWith(month) && parts.length == 2) {
      formatted += '/';
    }
  }

  if (parts.length > 2) {
    // Year - max 4 digits
    String year = parts[2];
    if (year.length > 4) {
      year = year.substring(0, 4);
    }
    formatted += '/$year';
  }

  /// Don't allow more than 3 parts (dd/mm/yyyy)
  if (parts.length > 3) {
    formatted = oldValue.text;
  }

  /// Limit total length (dd/mm/yyyy = 10 characters)
  if (formatted.length > 10) {
    formatted = formatted.substring(0, 10);
  }

  return TextEditingValue(
    text: formatted,
    selection: TextSelection.collapsed(offset: formatted.length),
  );
}