darttypecheckingruntime-type

What is the difference between using the is-operator and using the run-time type in Dart

I have worked through the dart codelab for iterables and stumbled upon this code fragment:

class EmailAddress {
  String address;

  EmailAddress(this.address);

  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
(a)          other is EmailAddress &&
(b)              runtimeType == other.runtimeType &&
                 address == other.address;
....

What is the difference between line (a) and line (b)? For me it seems like they do the same. Or more generally asked: What is the difference between using the is-operator and using the runtimeType property of an object for checking the run-time type in dart?

Solution

  • aSet is Iterable – this is true

    aSet.runtimeType == Iterable this is false

    So the is check handles subclasses.

    Also, we really recommend that you avoid using runtimeType. Especially when compiling to JavaScript. It can really blow up your compiled app size.

    I'll open an issue on that codelab!