react-notes/Redux.md

Intro to Redux

Lesson Objectives

1. Describe Redux
2. Install Redux
3. Create a reducer
4. Create a subscriber
5. Dispatch some actions
6. Move the store to a separate file

Describe Redux

• Redux acts as a third party that just deals with data so that the "state" of a model (e.g. a list of comments) doesn't have to be constantly passed around between react components
• Redux works on the publisher/subscriber model
  • a subscriber subscribes to Redux
  • any subscribers to Redux receive notification when Redux's data changes
  • the subscribers can then do what they want with the new "state" of Redux

Install Redux

Initialize the directory:

npm init

Create a main JS file:

touch index.js

Install Webpack:

npm install webpack --save-dev

Install Redux:

npm install redux --save-dev

Create a config for Webpack:

touch webpack.config.js

Add appropriate config code:

module.exports = {
    entry: './index.js',
    output: {
        filename: 'bundle.js'
    }
};

Set up NPM to run Webpack in package.json:

"scripts": {
  "build": "webpack"
},

Have index.js import createStore from redux

import { createStore } from 'redux';

console.log(createStore);

Test that import works:

npm run build
node dist/bundle.js

Create a reducer

A reducer will take an action and tell Redux how to alter its state. For now, write one in index.js

import { createStore } from 'redux';

const comments = function(state = [], action){ //this function must take these params
    switch(action.type){ //action must be an object that has a "type" property
        case 'ADD': //if the type of action is "ADD"
            return [...state, action.comment]; //return a copy of Redux's current state with the added comment
        default: //always have a default that returns the current state
            return state
    }
}

//now create a data store based on the custom reducer
const store = createStore(comments);

Create a subscriber

• Now let's create a subscriber in index.js that will be notified when our data store changes
• In the real world version of this example, this would probably be an HTML list that would update each time a new comment is made

//subscriber (e.g. an HTML list)
store.subscribe(function(){
    console.log(store.getState()); //for now just log what's in the store
});

Dispatch some actions

• In index.js, let's dispatch some actions, telling Redux how to change state:
• In the real world version of this example, this would probably be a user filling out an HTML form and submitting it

//publisher (e.g. an HTML form)
store.dispatch({
    type:'ADD',
    comment: {
        body:'this rox',
        author:'bob'
    }
});
store.dispatch({
    type:'ADD',
    comment: {
        body:'no, you rox',
        author:'sally'
    }
});
store.dispatch({
    type:'ADD',
    comment: {
        body:'we all rox',
        author:'zagthor'
    }
});

Compile:

npm run build

Run the code:

node dist/bundle.js

Move the store to a separate file

We want our data store in a separate file from our view logic

touch store.js

In store.js:

import { createStore } from 'redux';

const comments = function(state = [], action){
    switch(action.type){
        case 'ADD':
            return [...state, action.comment];
        default:
            return state
    }
}
export default createStore(comments);

Import the store in index.js:

import store from './store.js';

//subscriber (e.g. an HTML list)
store.subscribe(function(){
    console.log(store.getState())
});

//publisher (e.g. an HTML form)
store.dispatch({
    type:'ADD',
    comment: {
        body:'this rox',
        author:'bob'
    }
});
store.dispatch({
    type:'ADD',
    comment: {
        body:'no, you rox',
        author:'sally'
    }
});
store.dispatch({
    type:'ADD',
    comment: {
        body:'we all rox',
        author:'zagthor'
    }
});

Compile:

npm run build

Run the code:

node dist/bundle.js