flutter - Empty set state what is the point?

Question

I want to know the point behind calling setState without setting a new value to the variables.

  readLocal() async {
    prefs = await SharedPreferences.getInstance();
    id = prefs.getString('id') ?? '';
    if (id.hashCode <= peerId.hashCode) {
      groupChatId = '$id-$peerId';
    } else {
      groupChatId = '$peerId-$id';
    }

    setState(() {});
  }

Answer 1

I would say it's just a convention. The above can be re-written as

readLocal() async {
  prefs = await SharedPreferences.getInstance();
  setState(() {
    id = prefs.getString('id') ?? '';
    if (id.hashCode <= peerId.hashCode) {
      groupChatId = '$id-$peerId';
    } else {
     groupChatId = '$peerId-$id';
   }
  });
}

Both will do the same thing. Calling setState(() {}) after mutating the state variable looks neat and reabable.

As per the implementation section of setState, it will below things in order.

1. Assertions. If any assert fails, throws exception and stops there.
2. Execute the callback function (final dynamic result = fn() as dynamic;)
3. Ask framework to rebuild(_element.markNeedsBuild();)