parseOptionValue<R> method

R? parseOptionValue<R>(String name, R? tryParse(String))

Tries to parse an option value.

Returns null if the option was not supplied. Throws an ArgParserException if the option was supplied but is invalid.

Implementation

R? parseOptionValue<R>(String name, R? Function(String) tryParse) {
  var rawValue = this[name];

  String? stringValue;
  if (rawValue is bool) {
    // This function is meant to be used with options added with
    // [ArgParser.addOption], but try to handle boolean flags added with
    // [ArgParser.addFlag] as a precaution.
    stringValue = rawValue ? 'true' : 'false';
  } else {
    stringValue = this[name] as String?;
    if (stringValue == null) {
      return null;
    }
  }

  var value = tryParse(stringValue);
  if (value == null) {
    throw ArgParserException('Invalid value for "$name": "$stringValue"');
  }
  return value;
}