workshop 22: react-redux middleware
TRANSCRIPT
Previously in ReactJS...
ReactJS Basics
1. Decompose UI into reusable components which render to virtual DOM
2. ReactJS will sync VDOM to real browser DOM
3. JSX format
4. Can render on client and server
Previously in ReactJS...
Redux
PATTERNS
FLUX
CQRS
EVENT SOURCING
PRINCIPIOS
SINGLE SOURCE OF TRUTH
READ-ONLY STATE
CHANGES WITH PURE FUNCTIONS
Previously in ReactJS...
Redux
React Action Creator
Action
Reducers
State
Calls Returns
Sent to
Creates new
Sent to
Previously in ReactJS...
React-router
React
History
React router
Higher Order Components(HOC)
What is a HOC?
● It is a JavaScript function which is used for adding additional functionality to existing component
● A takes an existing component and returns another component that wraps it.
● If the HOC data changes, It will re-run again and update the resulting component.
● It usually contains reusable common behaviours resulting in simpler and better structured components.
● A component can be wrapped several times by multiple wrappers.
Decorator Pattern
Decorator Pattern
export default function(ComposedComponent) {
class HOCExample extends Component {
componentDidMount() {
this.setState({data:'Data from HOC...'});
}
render() {
return <ComposedComponent {...this.props} {...this.state} />;
}
}
return HOCExample;
}
HOC structure example
Redux Middleware
What is middleware
Provides capability to
put CODE
between
dispatching an action
and
reaching the reducer.
Basic redux life-cycle
React Action Creator
Action
Reducers
State
Calls Returns
Sent to
Creates new
Sent to
Redux life-cycle with middlewares
Middleware
React Action Creator
Action
Reducers
State
Calls Returns
Sent to
Forwards action to
Creates new
Sent to Middleware receives the action
and can log stop and modify it
Middleware benefits
COMPOSABLE
INDEPENDENT
Middleware stack example 1
Middleware # 1
I don’t care about this action, I’ll send it to the NEXT middleware
Action Creator Action
Reducers
nextMiddleware # 2
I will log this action, and move it forward
Middleware # 3
I don’t care about this action, I’ll send it to the NEXT middleware
next
console.log()
Middleware structure
● It is a function that receives the store
● It MUST return a function with arg “next”
● That returns a function with arg “action”
○ Where we do our stuff○ And return
■ next(action)■ state.dispatch(action)
export default function(store){
return function(next){
return function(action){
//do something
//use next(action) or
//state.dispatch(action)
}
}
}
Middleware structure
ES 5 middleware declaration
export default store => next => action => {
//do something
//next(action); or state.dispatch(action);
}
}
Middleware structure ES6
export default ({dispatch}) => next => action => {
//our stuff
}
}
src/middleware/myMiddleware.js
In case we don’t need the store
Middleware
C’MON MAN!
GIVE ME an EXAMPLE!!
Simplest example - logger
Middleware
REACT IncreaseCounter() INC_ACTION
ReducersSTATE- counter
Forwards action to
Component
counter+
- DecreaseCounter()
DEC_ACTION
Update state
counter
logger
Using our middleware
import {createStore, applyMiddleware } from 'redux';
import reducers from './reducers';
import MyMid from './middlewares/my-middleware';
const createStoreWithMiddleware = applyMiddleware(myMid)(createStore);
ReactDOM.render(
<Provider store={createStoreWithMiddleware(reducers)}>
<App />
</Provider>
, document.querySelector('.container'));
src/index.js
Modify action middleware workflow
Middleware that modifies specific action
Is it the action that I want?
Action Creator Action
no yes
Send action forwards
Next middleware
Do some stuff
Create new action with the results Action
Middlewarestack
next(action)store.dispatch(newAction)
Middleware
CAN YOU
SHOW ME
SOME CODE?
Dispatch action example - superstitious counter
Middleware
REACT IncreaseCounter() INC_ACTION
ReducersSTATE- counter
Forwards action to
Component
counter+
- DecreaseCounter()
DEC_ACTION
Update state
counter
logger
superstitious
Popular middlewares
redux-promise
redux-thunk
Redux-logger
Remember: npm install --save package
Thanks for your time!
Do you have any questions?
