This is a chapter in the Intro to Serverless guide.
Action and Reducer interfaces are defined in /lib/ObjectStore.ts:
// /src/lib/ObjectStore.ts
// Follows Flux Standard Actions (see https://github.com/redux-utilities/flux-standard-action)
export interface Action {
type: string,
payload?: { [key: string]: any },
meta?: { [key: string]: any },
error?: boolean
}
// pure function that produces new state (see https://redux.js.org/basics/reducers/#handling-actions)
export type Reducer<T> = (state: T, action: Action) => T;
export async function actionHandler<T>(store: ObjectStore<T>, id: string, action: Action, reducer: Reducer<T>): Promise<T> {
try {
let state = await store.get(id);
if (state) {
state = reducer(state, action);
return store.put(id, state);
} else {
return Promise.reject(`no item found with id ${id}`);
}
} catch(error) {
return Promise.reject(error);
}
}I have a file stubbed out called User.ts that looks like this:
// /src/User.ts
// TODO: add your own Actions
import { Action } from "./lib/ObjectStore";
// TODO: add your own fields
export default interface User {
id: string;
[key: string]: any;
}
// TODO: add your own Reducers
// This function is called when a user sends an action to the `/user/self/action`
export function rootReducer(state: User, action: Action): User {
return state;
}I have had great success using uni-directional dataflow patterns to manage the state of an object. This includes the global state of a mobile or front-end web application, or a single object like a user or an IoT device. My use of it in a back-end framework is a bit unique, and it is not intended for a wide variety of applications, just updating single objects that are stored as a single document. Here is a good article from the React world on its pros and cons: https://medium.com/@dan_abramov/you-might-not-need-redux-be46360cf367
To implement this pattern to update your user object, here are some tutorials you can follow (note: just follow the action and reducer part of the tutorials):
- Actions and Reducers guides from Redux (ignore the rest):
- Pure functions: https://medium.com/@jamesjefferyuk/javascript-what-are-pure-functions-4d4d5392d49c