Correct TypeScript typing example for Redux Thunk actions

redux-actions.ts

import {Action, ActionCreator, Dispatch} from 'redux';
import {ThunkAction} from 'redux-thunk';

// Redux action
const reduxAction: ActionCreator<Action> = (text: string) => {
  return {
    type: SET_TEXT,
    text
  };
};

// Redux-Thunk action
const thunkAction: ActionCreator<ThunkAction<Action, IState, void>> = (
  text: string
) => {
  return (dispatch: Dispatch<IState>): Action => {
    return dispatch({
      type: SET_TEXT,
      text
    });
  };
};

// Async Redux-Thunk action
const asyncThinkAction: ActionCreator<
  ThunkAction<Promise<Action>, IState, void>
> = () => {
  return async (dispatch: Dispatch<IState>): Promise<Action> => {
    try {
      const text = await Api.call();
      return dispatch({
        type: SET_TEXT,
        text
      });
    } catch (e) {}
  };
};

How do you use the action which returns a thunk later? I cannot feed it into dispatch function in mapDispatchToProps, since the action creator returns a function (a thunk), and not an action (it doesn't have type property on it).

const mapDispatchToProps = (dispatch: Dispatch, ownProps: OwnProps): DispatchProps => {
  return {
    handleAsyncAction: () => {
      dispatch(Actions.HomePage.asyncFetch())
    },
  }
}

(140,16): Argument of type '(dispatch: Dispatch<AnyAction>) => Promise<void>' is not assignable to parameter of type 'AnyAction'.
  Property 'type' is missing in type '(dispatch: Dispatch<AnyAction>) => Promise<void>'.

I can make it work at runtime by casting to any, but ew.

@lazarljubenovic same problem here...

@milankorsos how did you resolve this case?

@lazarljubenovic after some time, I found a solution... here is what I'm doing:

import { connect } from 'react-redux';
import { Action } from 'redux';
import { ThunkDispatch } from 'redux-thunk';
import { MyState } from '../my-store/state';
​​
// ...

const mapDispatchToProps = (dispatch: ThunkDispatch<MyState, void, Action>) => {
  return {
    onRequestClick: (arg: any) => dispatch(myAsyncAction(arg)),
  };
}
​
function myAsyncAction(arg: any) {
  return async (dispatch: ThunkDispatch<MyState, void, Action>) => {

    dispatch(requestDataStartAction(arg));
​
    let result: string;

    try {
      result = await fetch('/url', { data: arg });
    }
    catch (error) {
      dispatch(requestDataErrorAction(arg, error));
      return error;
    }
    
    dispatch(requestDataSuccessAction(arg, result));
  }
}

export default connect(
  mapStateToProps,
  mapDispatchToProps
)(MyComponent)
​

I ran across this trying to find an example of using redux-thunk with typescript. The only thing missing from the examples above is how to type getState.
I opened an issue on redux-thunk, but did not receive much help: reduxjs/redux-thunk#213 (comment)

Also, in my use case, I am dispatching things before and after the promise resolves.

The response from timdorr pointed at the tests, which are quite helpful actually. From those tests, I picked up a pattern that works pretty well. In my main reducers file (where I pull together types for all of the actions and state slices), I'll export a few types for use elsewhere in the application:

export type ThunkResult<R> = ThunkAction<R, IStoreState, null, IStoreActions>

export type ThunkDispatch = ThunkDispatch<IStoreState, null, IStoreActions>

export default combineReducers<IStoreState, IStoreActions>({
  // various reducers
})

When defining an async thunk action, they'll use ThunkResult<R> as the return type, this looks like this:

export function someAction1(): ThunkResult<void> {
  return (dispatch, getState) => {
    // do da dispatch
    // also `getState` is typed as `() => IStoreState`
  }
}

This also works with async functions (and by nature, promise.then works):

export function asyncAction2(): ThunkResult<Promise<boolean>> {
  return async (dispatch, getState) => {
    await someThing()
    return true
  }
}

export function asyncAction3(): ThunkResult<void> {
  return (dispatch, getState) => {
    dispatch(asyncAction2()).then(result => assert(result))  // no type errors!
  }
}

When using mapDispatchToProps, I'll use ThunkDispatch.... this only seems necessary when getting dispatch through react-redux -- if I have a reference to the store, the dispatch action seems to come with the additional typings for handling dispatches with thunks fine.... pulling it all together for a connected container --

const selector= createSelector((state: IStoreState) => state.someSlice, slice => ({slice}))

const mapDispatchToProps = (dispatch: ThunkDispatch): ComponentActionProps => ({
  handleDrawCard: () => dispatch(asyncAction()) // works fine, even with no {type: string} on asyncAction
})

const mapStateToProps = (state: IStoreState): ComponentConnectedProps => selector(state)

export const Container = connect(mapStateToProps, mapDispatchToProps)(ContainerComponent)

Hey, @tswaters!

I'm also trying to tie-up Typescript with React/Redux/Thunk/etc 😃

For those who are just like me, one should mention that at first, you need to import all the stuff:

import { ThunkAction, ThunkDispatch } from 'redux-thunk';

Thank you! 👍

these types might be useful to people using react 4 & redux thunk 2.3.

for typing thunks

ActionCreator<ThunkAction<Promise<any>,IState,null,AnyAction>>

where Promise<any> is an example of return type of the thunk
and AnyAction is the type of action you'll dispatch

and for typing dispatch

ThunkDispatch<IState, null, AnyAction>

similar arguments, see source of redux-thunk

This works when I pass mapDispatchToProps as a function.

impression IProps {
thunkAction: (arg: IArg) => Promise<IArg>
}
class Comp extends React.Component<IProp> { ... }

const mapStateToProps = ...
const mapDispatchToProps = (dispatch: ThunkDispatch<IState, any, IAction>) => ({
  thunkAction: (arg: Partial<IArg>) =>
    dispatch(thunkAction(arg))
});
connect(mapStateToProps, mapDispatchToProps)(Comp);

Doesn't work when I pass it as an object

//  Type 'ThunkAction<Promise<ThunkAction>, IState, any, IAction<any>>' is not assignable to type 'Promise<IArg>'.
connect(mapStateToProps, { thunkAction })(Comp);

Whats missing here?

As @aaronlifton2 mentioned up above it looks like the type signature for ThunkAction has changed in newer versions of redux-thunk.

export type ThunkAction<R, S, E, A extends Action> = (
  dispatch: ThunkDispatch<S, E, A>,
  getState: () => S,
  extraArgument: E
) => R;

Here's an example of how I set up my Thunk types: https://gist.github.com/seansean11/196c436988c1fdf4b22cde308c492fe5

@tswaters

export type ThunkResult<R> = ThunkAction<R, IStoreState, null, IStoreActions>

Thank you!

This works when I pass mapDispatchToProps as a function.

impression IProps {
thunkAction: (arg: IArg) => Promise<IArg>
}
class Comp extends React.Component<IProp> { ... }

const mapStateToProps = ...
const mapDispatchToProps = (dispatch: ThunkDispatch<IState, any, IAction>) => ({
  thunkAction: (arg: Partial<IArg>) =>
    dispatch(thunkAction(arg))
});
connect(mapStateToProps, mapDispatchToProps)(Comp);

Doesn't work when I pass it as an object

//  Type 'ThunkAction<Promise<ThunkAction>, IState, any, IAction<any>>' is not assignable to type 'Promise<IArg>'.
connect(mapStateToProps, { thunkAction })(Comp);

Whats missing here?

Has this been solved yet? I get a similar error when trying to use the object form of mapDispatch; using the function form works fine.

Unless I'm missing something obvious, this is a rather sharp edge :(

Following the introductory Redux docs, you are guided to prefer the object form of mapDispatch, and then in the typescript section, you are introduced the ThunkDispatch type, which doesn't work with the object form of mapDispatch.

I am migrating to Typescript for fun, but I am not understanding how I can avoid all the boilerplate when I am writing my actions and reducers like this:

localUserReducer.js

const initialState = {
  fetching: false,
  fetched: false,
  user: undefined,
  errors: undefined,
};

export default function (state = initialState, action) {
  switch (action.type) {
    case 'GET_USER_PENDING':
      return {
        ...state,
        fetching: true,
      };
    case 'GET_USER_FULFILLED':
      return {
        ...state,
        fetching: false,
        fetched: true,
        user: action.payload,
      };
    case 'GET_USER_REJECTED':
      return {
        ...state,
        fetching: false,
        errors: action.payload,
      };
    default:
      return state;
  }
}

localUserActions.js

import axios from 'axios';

export const getUser = () => async (dispatch) => {
  dispatch({ type: 'GET_USER_PENDING' });
  try {
    const { data } = await axios.get('/api/auth/local/current');
    dispatch({ type: 'GET_USER_FULFILLED', payload: data });
  } catch (err) {
    dispatch({ type: 'GET_USER_REJECTED', payload: err.response.data });
  }
};

Would I be expected to write an interface for each _PENDING, _FULFILLED, and _REJECTED action?

I may have a huge misunderstand of redux-thunk as I am a newbie. I don't understand how I can send _REJECTED actions if I use the implementation of Typescript and redux-thunk documented here: https://redux.js.org/recipes/usage-with-typescript#usage-with-redux-thunk

export type ThunkResult<R> = ThunkAction<R, IStoreState, null, IStoreActions>

Just want to say thank you, I struggled with it and your answer helped me solve the problem. 😄

Thanks @milankorsos!

Please hellp me )))

export type ThunkResult2<R> = ThunkAction<R, AppStateType, null, Action>
export type ThunkDispatch2 = ThunkDispatch<AppStateType, null, Action>

export const login = (auth: any): ThunkResult2<Promise<{a: boolean, b: string}>> => async (dispatch: ThunkDispatch2) => {
    const res =  await AuthApi.authentication(auth);
    const r = dispatch(AuthActions.login(new Auth({ ...res })));
    return {
        a: true,
        b: '123'
    } // this very well work
}

// but
......

            onSubmit={ async (values) => {
                const res = await dispatch(login(values))
                console.log(res.a) // this problem
            }}

TS2339: Property 'a' does not exist on type 'ThunkAction { a: boolean; b: string; }>, CombinedState{ auth: never; }>, null, Action >'

I still can't locate IStoreState

Maybe this is right place to use "any" when i must make type for thunk action in my props.