redux-persist の flow 型付け

Action の型に Union しておきます。

src/types/index.js

import type { Action as _Action } from './action'
import type { State as _State } from './state'

type RehydrateAction = {
  type: 'persist/REHYDRATE',
  payload: _State,
}

export type State = _State
export type Action = _Action | RehydrateAction

reducer などで action.payload を State type として使えます。

src/containers/System/reducer.js

// @flow
import { REHYDRATE } from 'redux-persist/constants'

import type { Action, System } from '../../types'
import { Actions } from './actionTypes'

export type State = System

export const initialState: State = {
  selectedTab: 1,
}

export default function(state: State = initialState, action: Action): State {
  switch (action.type) {
    case Actions.SWITCH_TAB:
      return {
        ...state,
        selectedTab: action.target,
      }
    case 'persist/REHYDRATE':
      return action.payload.System

    default:
      return state
  }
}

akameco/s2s-examples のプロジェクト構成に導入する例にしています。