Redux Epics：类型不匹配

Question

我正在尝试将我的Firestore与Redux同步。我使用以下内容：

  redux: "^3.0.0"
  flutter_redux: "^0.5.0"
  redux_logging: "^0.3.0"
  redux_epics: "^0.9.0"
  rxdart: "^0.16.7"

当我尝试将我的史诗添加到中间件时，我在这行代码中得到了这个错误：

final allEpics = combineEpics<AppState>([
    ordersEpic,
  ]);

  

[dart]元素类型＆＃39;（Stream，EpicStore）→流＆＃39;无法分配到列表类型＆＃39;（Stream，EpicStore）→流＆＃39;。

史诗：

Stream<dynamic> ordersEpic(Stream<OrdersOnDataEventAction> actions, EpicStore<AppState> store){
  return Observable(actions)
  .ofType(TypeToken<RequestOrdersDataEventsAction>())
  .switchMap((RequestOrdersDataEventsAction requestOrders){
    return getOrders()
    .map((orders)=>OrdersOnDataEventAction(orders))
    .takeUntil(actions.where((action)=>action is CancelOrdersDataEventsAction));
  });
}
Observable<List<DocumentSnapshot>> getOrders(){
  return Observable(Firestore.instance.collection("orders").snapshots())
  .map((QuerySnapshot q)=>q.documents);
}

操作

class RequestOrdersDataEventsAction{}

class CancelOrdersDataEventsAction{}

class OrdersOnDataEventAction{ 
  final orders;
  OrdersOnDataEventAction(this.orders);
 }

订单

final ordersReducer = combineReducers<List<DocumentSnapshot>>([
  TypedReducer<List<DocumentSnapshot>,OrdersOnDataEventAction>(_setOrders)
]);

List<DocumentSnapshot> _setOrders(List<DocumentSnapshot> oldOrders, OrdersOnDataEventAction action){
  return action.orders;
}

Answer 1

这听起来像是一个协方差问题。

typedef void myType(Stream<dynamic> s);

final list = List<myType>();

void myFunction(Stream<Order> s) {}
void myOtherFunction(Stream<dynamic> s) {}

// This gives the "(Stream<Order>) -> void not of expected type (Stream<dynamic>) -> void" error
list.add(myFunction);  
// This works
list.add(myOtherFunction);

您是否尝试将动作参数的类型更改为动态？

Stream<dynamic> ordersEpic(Stream<dynamic> actions, EpicStore<AppState> store){