operator [] method

String operator [](String key)

Retrieves a single fully sanitized value for the key.

Values are always processed according to the ParamsMode.standard mode. That is, all whitespaces (including line terminators) are converted into spaces (U+0020); multiple spaces are collapsed into a single space; and spaces at either ends are trimmed. To use other modes, use the values method.

The empty string will be returned if:

• there is no value matching the key;
• there is a value but it only contains whitespace; or
• there is a value that contains zero characters.

If there is a need to distinguish between these different values, use the values method instead.

This operator must only be used for parameters which are single valued. If the key matches multiple values: in production mode, the empty string is returned; in checked mode, an assertion error is raised. Use the values method for keys with multiple values.

Implementation

String operator [](String key) {
  final values = _data[key];
  if (values == null) {
    return ''; // no value for key
  } else if (values.length == 1) {
    // Single value
    return _sanitize(values[0], ParamsMode.standard);
  } else {
    assert(values.length == 1, 'multi-valued: do not use [] with "$key"');
    return ''; // error value
  }
}