react-redux-scaffold

A WIP project to learn React+Redux concepts, and setup a project scaffold.

Largely adopted from: https://www.valentinog.com/blog/redux/

Install, run

npm install
npm start

File structure:

• /src
  • /js
    • /actions action object definitions
    • /components react UI components
    • /constants e.g. action type string defs
    • /middleware custom middleware components, e.g. to validate an action payload before it's passed to a reducer
    • /reducers redux reducer components
    • /store redux store definition
    • index.js initialises react app wired to redux (Provider wraps up your React application and makes it aware of the entire Redux’s store)
  • index.html root html entry point
  • index.js root js entry point

Resources

• Redux testing with Jest
• React Web Router

Oversimplified explanation of concepts

• React
  • Rendering of UI components
    • Ideally I want to move to use the Presentation/Container pattern, but first - baby steps.
  • Wiring of events and state to Redux components
  • Routing (react-router)
• Redux
  • All the state things
  • Store
    • The redux store is fundamental: the state of the whole application lives inside the store.
  • Reducers
    • The state in redux comes from reducers, reducers produce the state of your application
    • A reducer is just a JavaScript function. A reducer takes two parameters: the current state and an action
    • The reducer calculates the next state depending on the action type. Moreover, it should return at least the initial state when no action type matches.
  • Actions and Action creators
    • In redux, an action is a simple object with a type, and a payload, e.g.
      • { type: 'LIKE_POST', payload: { POST_ID: 123 } }
    • An action creator is a function that may contain some logic, which is called by a reducer /src/js/actions/**.js
  • Middleware
    • Redux middleware is code (a funciton) that intercepts actions coming into the store via the dispatch() method.
    • Middlewares in Redux are super important because they will hold the bulk of your application’s logic. The nice thing is that while inside the middleware you can access getState and dispatch
  • react-thunk
    • By default, we can’t use action creators for async tasks because they are expected to return an object (i.e. not a promise/callback function).
    • redux-thunk middleware is used to solve this problem.

What is actually happening when I add a post?

• The PostForm component is connected to Redux
  • It maps the addArticle action to the Redux dispatch API method and binds to the forms onSubmit event.
• When you click the submit button:
  • onSubmit event fired, triggers handleSubmit
  • handleSubmit uses a local (non Redux) state to grab the post title and use to trigger the addArticle action in its props
  • this.props.addArticle is mapped to Redux dispatch method so it triggers the addArticle action
  • the store has been configured with forbiddenWordsMiddleware, so the action is processed here first.
    • if a forbidden word is detected, adding the article is blocked and a message shown
    • else if valid article
      • the action passed through to the reducer, which returns a new copy of the state which contains the new article paylod (no mutation!)

Tip: use Redux DevTools

• Great tool to allow you to see exactly what's happnening under the hood
• Timetravel!