Wrapping reducer in handleAction throws undefined state

[Bartvds]

If I wrap a reducer in handleAction I get this error:

"Reducer "selectedReddit" returned undefined during initialization. If the state passed to the reducer is undefined, you must explicitly return the initial state. The initial state may not be undefined."

If I debug I see redux tries to get a initial state by calling the wrapped reducer with undefined state and a specific system action type. Because the type does not match the wrapped one the inner reducer never runs and no state default is created.

If I use handleActions (m) with default state it works fine. Same function with default state in arguments and classic action-type check is also fine.

Anyway,is handleAction usable like this? Readme doesn't really specifiy use case.

[iest]

Got this error too. Using handleActions instead and passing a default state worked for me as well.

[yoavniran]

yup, running into this as well. Seems like handleAction is broken with initial state being undefined...

[drhayes]

Happening for me too. Same workaround.

I'm getting it because I'm passing the resultant reducer to combineReducers from redux. It aggressively "ensures reducer sanity" by passing undefined initially. Third arg, maybe?

[tony-kerz]

i get this:

Uncaught Error: Reducer "loginReducer" returned undefined during initialization. If the state passed to the reducer is undefined, you must explicitly return the initial state. The initial state may not be undefined.

from this:

export const loginReducer = handleAction(
  actions.LOGIN,
  (state={}, action) => {
    return {
      ...state,
      session: {
        active: true
      }
    }
  }
)

this is with redux-actions 0.8.0 (alongside of redux-promise 0.6.0-alpha if it matters)

i'm assuming this is the same issue...

[talarari]

Getting the same error , should be possible to do this:
const connectionState = handleAction("connect", (state= 'disconnected',action)=> 'connecting')
const rootReducer = combineReducers({
connectionState
})

[apisurfer]

Same problem here when I define reducers with handleAction and then try to combine them with combineReducers from redux. They go through internal combineReducers sanity check that calls them without passing an state or action an that crashes the function

[saiichihashimoto]

Same

[danny-andrews]

+1, this function is unhelpful as it stands.

[emiloberg]

For others finding their way in here:

Note that handleActions (plural) works but wants the default state as the second argument to handleActions. As can be seen in the readme or in this example

const initState = {};
const aReducer = handleActions({
    SOMETHING: (state, action) => ({
        //do stuff
    })
}, initState);

const reducers = combineReducers({
    aReducer
});

[lsunsi]

Same problem. So handleAction is practically unusable, right?

[timche]

I don't know since when Redux is doing this sanity check, but without an initial state, handleAction is definitely unusable.

Nevertheless, #55 adds support for that.

[evenfrost]

Looking forward to this as well, going through the Redux tutorial and handleAction bundled with combineReducers throws the error.

[yangmillstheory]

@timche isn't this closed with 0.10.0?

[timche]

Thanks for the reminder @yangmillstheory 👍

[vtvz]

Solution:

const someReducer = handleAction(someAction, (state, {payload}) => {
    return {
        ...state,
        ...payload,
    };
}, {}); // <-- default state

The reason why this should be like this. Third param in handleAction should not be empty.

[KalidassM01]

You have to add default: return state; at the bottom of all cases of your switch function. Hope this work. Good luck