Bloc: Is there any way to type cast state?

[dungnv2602]

My experience with bloc so far is amazing, but the only issue that annoys me is whenever I want to get the current state I always have to check it in a condition and then define another variable which typecast state. Like this:
if(state is StateSuccess){ final success = state as StateSuccess; }
Is there another way to work around this issue?

[dungnv2602]

@ReversedHourglass Yeah, this the only annoyance when working with bloc

[ram231]

Well, That was the reason why it is Predictable because you know which state is currently active in the Bloc.

You'll still be doing the same way as a StreamBuilder or FutureBuilder where you catch a lot of

if(!snapshot.hasData){
 return LoadingWidget();
}
if(snapshot.hasError){
return Text("Error occured");
}

[dungnv2602]

@ram231 The problem with bloc is I have to define a separated local variable to assign type casted version of state. Meanwhile in the wrapping condition checking already check that. This is what I expected:

if(state is StateSuccess)
{
'do something with state since it is already is StateSucces, don't need to assign to another variable'
}

[ram231]

@ram231 The problem with bloc is I have to define a separated local variable to assign type casted version of state. Meanwhile in the wrapping condition checking already check that. This is what I expected:

if(state is StateSuccess)
{
'do something with state since it is already is StateSucces, don't need to assign to another variable'
}

Is this inside the mapEventToStste or Is it in the Bloc builder Widget?

[felangel]

HI @dungnv2602 👋
Thanks for opening an issue!

The reason you're having this issue is because the state property on bloc is a computed property and can change at any time so just because state is StateSuccess at time x does not guarantee state is StateSuccess at time y.

As a result, you can just save a snapshot of state before doing the typechecking like:

Stream<MyState> mapEventToState(event) async* {
  final currentState = state;
  if (currentState is StateSuccess) {
    // no type casting required
    doSomethingWith(currentState.someProperty);
  }
}

Another tip is to break out your mapEventToState into private helpers and you can inject state into those helpers like:

Stream<MyState> mapEventToState(event) async* {
  if (event is SomeEvent) {
    yield* _mapSomeEventToState(event, state);
  }
}

Stream<MyState> _mapSomeEventToState(SomeEvent event, MyState state) async* {
  if (state is StateSuccess) {
    // no type casting needed
    doSomethingWith(state.someProperty);
  }
}

Hope that helps 👍

[dungnv2602]

@felangel Thank you, the #1 tip is nice, but we still have to assign it into another variable. But now I understand the reason why, guess we have to live along with it.