actions.ts

// store/session/actions.ts

import { AnyAction } from 'redux';

export interface SetAction {
  type: 'SET'
  accessToken: string
}

export interface Fetching {
  type: 'SET_FETCHING'
  isFetching: boolean
}

export type Action = SetAction | Fetching

export const set = (accessToken: string): SetAction => {
  return { type: 'SET', accessToken }
}

export const isFetching = (isFetching: boolean): Fetching => {
  return { type: 'SET_FETCHING', isFetching }
}

index.ts

// store/index.ts

import { createStore, combineReducers, applyMiddleware } from 'redux'
import sessions, { State as SessionsState } from './session/reducers'

export interface RootState {
  sessions: SessionsState
}

export default createStore(combineReducers({
  sessions
}))

reducers.ts

// store/session/reducers.ts

import { combineReducers } from 'redux'

import { Action } from './actions'

export interface AccessToken {
  isFetching: boolean
  accessToken?: string
}

export interface State {
  accessToken: AccessToken
}

const accessToken = (state = { isFetching: false }, action: Action): AccessToken => {
  switch (action.type) {
  case 'SET':
    return { ...state, accessToken: action.accessToken }
  case 'SET_FETCHING':
    return { ...state, isFetching: action.isFetching }
  }
  return state
}

export default combineReducers<State>({
  accessToken
})