combineReducers doesn't infer type

Question

I am using combineReducersin my React TypeScript app:

// combinedReducer.ts
import { combineReducers } from \'redux\'
import reducer1 from \'./r         


        

Answer 1

Same problem for me using redux 4.0.5 and typescript 4.0.1. Had to write a inferrer myself:

type BaseReducerMap = {
    [K in keyof S]: (state: S[K], action: any) => S
}

export type InferRootState, S = any> = {
    [K in keyof ReducerMap]: ReturnType
}

Then for your set of reducers (before you combine them)

const reducers = {
    login: loginReducer,
    chatUsers: chatUsersReducer,
};
const combinedReducer = combineReducers(reducers);

export type State = InferRootState;

Then typescript can successfully infer the type of my State. I don't know why it fails in this version.