Add a generic reducer factory automatically handling async-actions - createAsyncReducer

[lajtmaN]

Is your feature request related to a problem?

It would be awesome to be able to build reducer factories which are based on async actions, that can in a generic way handle the payloads of that async action.

Who does this impact? Who is this for?

All users - as an example you could create an async action and create a reducer with a simple one liner for simple reducers like loading and error.

Example

The following example utilizes that all async failure actions return an Error object.

export const fetchCurrentUserActions = createAsyncAction(...)<void, FetchCurrentUserDetailsResponse, Error>();


export const currentUserReducer = combineReducers<CurrentUserState>({
  loading: createLoadingReducer(fetchCurrentUserActions), // <---- Nice one line reducer
  error: createErrorReducer(fetchCurrentUserActions), // <---- Nice one line reducer
  ....
});

export const createErrorReducer = <TSuccess>(
  asyncAction: AsyncActionBuilder<any, any, any, any, TSuccess, Error>
): Reducer<ErrorState> => 
  (state = null, action: ActionType<typeof asyncAction>) => {
    switch (action.type) {
      case getType(asyncAction.failure):
        return action.payload; // <---- action is not narrowed after getType(), thus .payload doesn't exist on action or isn't of type Error as expected
      case getType(asyncAction.success):
        return null;
      default:
        return state;
    }
  };

My createLoadingReducer does not care about any payloads thus my reducer function just takes an AnyAction

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[ecnaidar]

Hey,
this would be very nice fix have, currently typecasting things manually after the switch and although it works, leaves room for error and verbose.
Is this related to piotrwitek/react-redux-typescript-guide#121 ?
If so, probably possible to replace custom factories with one that will be added from that issue.

[lajtmaN]

I don't think typecasting is a solution since this is such a generic reducer, that it needs to handle the types correctly before the concept can be widely used.
When piotrwitek adds some documentation on how the partial reducers will work I will try to give this reducer factory a spin again with that method.

[IssueHuntBot]

@IssueHunt has funded $75.00 to this issue.

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[issuehunt-oss]

@sposterkil has funded $20.00 to this issue.

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