Type assertion on the whole action

[farzadmf]

Hi,

I just found out about your library, and I think it is what I have been looking for to substantially reduce boilerplate code for actions and action creators; thank you!

Creating actions (using createAction) and switching on them (using getType) in the reducer works fine, but I was wondering if there's a way to do type checking for a method that expects a specific kind of action.

Example of my actions (I'm using lodash for values and map):

export enum ActionTypes {
  GetCameras = 'GET_CAMERAS',
  GetCamerasSuccss = 'GET_CAMERAS_SUCCESS',
}

export const cameraActions = {
  getCameras: createAction(ActionType.GetCameras, ( /*...*/ ) => ({
    type: ActionTypes.GetCameras,
    /* payload: ... */
  }),
  getCamerasSuccess: createActionTypes.GetCamerasSuccess, (/*...*/) => ({
    type: ActionTypes.GetCameras,
    /* payload: ... */
  }),
};

const returnsOfActions = _.map(_.values(actions), $call));
export type CameraAction = typeof returnsOfActions[number];

Maybe a good example would be a case where the reducer wants to call another method for a specific action type, for example, in my reducer:

export const reducer = (state = initialState, action: CameraAction) => {
  case getType(cameraActions.getCameras):
    return state; /* ... */
  case getType(cameraActions.getCamerasSuccess):
    return receiveCameras(state, action);
  default:
    return state;
};

Now, in my receiveCameras method, I want to make sure the second argument is of type cameraActions.getCamerasSuccess.

I can do something like this:

const receiveCameras = (state: CameraState, action: CameraAction) => {
  if (action.type !== getType(cameraActions.getCamerasSuccess)) {
    return;
  }
  
  // Now my action type is correct
}

I was wondering if I can specify the type when defining the parameter in the method to avoid doing that if check

Thank you

[piotrwitek]

Hello @farzadmf
Currently not but it's because of TS v2.7 inference engine limitation.
Fortunately you will be able to do that with the new API in v2.0 I'm currently working on.

type CameraAction = ReturnType<typeof cameraActions.getCamerasSuccess>;
const receiveCameras = (state: CameraState, action: CameraAction) => {
...

I will open issue today for discussion/feedback on the API 2.0, new features like Symbols support, but also improvements to createAction (got rid of duplicated type argument finally :)) and probably push the working implementation to the next branch for testing.

EDIT: API v2.0 discussion here: #22

[farzadmf]

Hello @piotrwitek thank you for your answer, So how I can I keep track of the new API version you mentioned and when it will available?

[piotrwitek]

2 days top I think, I'm heavily working on it

[dziamid]

Looking forward to start using ReturnType. Can I just update TS to 2.8@rc and start using ReturnType with typesafe-actions?

[duro]

@dziamid I have done so with success. I have a saga that looks like this:

import { sessionActions as SA } from './actions'

function* setToken(action: ReturnType<typeof SA.setToken>) { }

Where SA.setToken is an action that was built with typesafe-actions

[dziamid]

@duro, sweet, was looking for the exact same use case. Are you using the version 1 of this library?

[duro]

Yes. I too am eager to see v2. I've been playing with TS2.8 and I can totally see how it's going to make this library better.

…

On Thu, Mar 22, 2018 at 1:08 AM Dziamid ***@***.***> wrote: @duro <https://github.com/duro>, sweet, was looking for the exact same use case. Are you using the version 1 of this library? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#19 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AABE4Ex-60V1UJtIGOsetAgtayx8sAJbks5tg1wGgaJpZM4SlU3y> .

[dziamid]

How exactly? Type and payload assertions are all I care about right now.

[piotrwitek]

Hi @dziamid, for example this: #21 (comment)

[piotrwitek]

Closing as issue seems to be unactionable.