toDouble method
Converts a numeric string to a double. Returns null if parsing fails or string is empty.
Implementation
double? toDouble() {
if (this == null) return null;
final regex = RegExp(r'^-?\d*\.?\d*');
final match = regex.firstMatch(this!);
final numericString = match?.group(0);
if (numericString == null || numericString.isEmpty) return null;
return double.tryParse(numericString);
}