Flutter：如何将数据从"Stream<Foo？>"过滤到"Stream<Foo>"

Question

我需要在我的插件中从EventChannel创建一个新的Stream<Foo>，我尝试这样做，但我有Stream<Foo?>，我必须为过滤所有空值并返回为Stream<Foo>做什么

Stream<Foo> get getStream {
return _eventChannel
.receiveBroadcastStream()
.map<Foo?>((dynamic status) {
assert(
status is int,
'status should be int, but it is ${status.runtimeType}',
);
if (status is int) {
return FooStatus.valueOf(status); // can be null
}
}).helpMeFiltredLikeThis<Foo>((Foo? value) => value != null); // how i can do some like this
}

Answer 1

您可以在结尾处使用cast:

final nonNullableStream = nullableStream.cast<Foo>();