This is continuation of return type for getter problem when returning enum.
When I am using enum (enum.enum_value.name) I am getting an error however when I use static const String the code builds fine.

I created a variable of enum.enum_value.name (SerialPortParity.none.name), it is creating a variable of type String.

final returnVal = SerialPortParity.none.name;

I am unable to understand this behavior.
https://dart.dev/tools/diagnostic-messages?utm_source=dartdev&utm_medium=redir&utm_id=diagcode&utm_content=getter_not_subtype_setter_types#getter_not_subtype_setter_types

If I am getting the error The return type of getter 'parity' is 'String' which isn't a subtype of the type 'SerialPortParity' of its setter 'parity'. then why I am not getting the same error when I return static const String

Running Code :

  static const String parityNone = 'None';
  static const String parityEven = 'Even';
  static const String parityOdd = 'Odd';
  static const String parityMark = 'Mark';
  static const String paritySpace = 'Space';

  int _parity = UsbPort.PARITY_NONE;
  String get parity {
    switch (_parity) {
      case UsbPort.PARITY_NONE:
        return SerialPort.parityNone;
      case UsbPort.PARITY_EVEN:
        return SerialPort.parityEven;
      case UsbPort.PARITY_ODD:
        return SerialPort.parityOdd;
      case UsbPort.PARITY_MARK:
        return SerialPort.parityMark;
      case UsbPort.PARITY_SPACE:
        return SerialPort.paritySpace;
      default:
        return SerialPort.parityNone;
    }
  }

  set parity(String parity) {
    switch (parity) {
      case SerialPort.parityNone:
        _parity = UsbPort.PARITY_NONE;
        break;
      case SerialPort.parityEven:
        _parity = UsbPort.PARITY_EVEN;
        break;
      case SerialPort.parityOdd:
        _parity = UsbPort.PARITY_ODD;
        break;
      case SerialPort.parityMark:
        _parity = UsbPort.PARITY_MARK;
        break;
      case SerialPort.paritySpace:
        _parity = UsbPort.PARITY_SPACE;
        break;
      default:
        //No Change
        break;
    }
  }

Error Code :

enum SerialPortParity {
  none,
  even,
  odd,
  mark,
  space,
}

 int _parity = UsbPort.PARITY_NONE;
  String get parity {
    switch (_parity) {
      case UsbPort.PARITY_NONE:
        return SerialPortParity.none.name;
      case UsbPort.PARITY_EVEN:
        return SerialPortParity.even.name;
      case UsbPort.PARITY_ODD:
        return SerialPortParity.odd.name;
      case UsbPort.PARITY_MARK:
        return SerialPortParity.mark.name;
      case UsbPort.PARITY_SPACE:
        return SerialPortParity.space.name;
      default:
        return SerialPortParity.none.name;
    }
  }

set parity(SerialPortParity parity) {
    switch (parity) {
      case SerialPortParity.none:
        _parity = UsbPort.PARITY_NONE;
        break;
      case SerialPortParity.even:
        _parity = UsbPort.PARITY_EVEN;
        break;
      case SerialPortParity.odd:
        _parity = UsbPort.PARITY_ODD;
        break;
      case SerialPortParity.mark:
        _parity = UsbPort.PARITY_MARK;
        break;
      case SerialPortParity.space:
        _parity = UsbPort.PARITY_SPACE;
        break;
      default:
        //No Change
        break;
    }
  }

Error :

The return type of getter 'parity' is 'String' which isn't a subtype of the type 'SerialPortParity' of its setter 'parity'.
Try changing the types so that they are compatible.

CodePudding user response：

Setter and Getter must use the same Type.

In your case, either a String or an Enum.

One cannot mix these:

String get parity {} // STRING

set parity(SerialPortParity parity) {} // ENUM

Consider the following, disfunctional code, which also uses both types for the same variable.

This is how it looks to Dart when one defines a Getter and Setter with not-matching Types:

// Will not compile, as parity can be of one Type only.
class Abc {
  String parity;
  SerialPortParity parity;
}


var abc = Abc();
abc.partity = x;
var z = abc.partity;