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redux.tex
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redux.tex
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\section{\texorpdfstring{\includegraphics[width=150pt]{redux.png}}{Redux}}
\begin{frame}
\frametitle{Redux}
Redux is a predictable state container for JavaScript apps.
\textbf{Three Principles}
Single source of truth
State is read-only
Changes are made with pure functions
\end{frame}
\begin{frame}
\frametitle{Architecture of a redux app}
\includegraphics[width=\textwidth]{redux-unidir-ui-arch.png}
\end{frame}
\begin{frame}[fragile]
\frametitle{Actions}
Payloads of information that send data from your application to your store. They are the only source of information for the store. You send them to the store using \textit{store.dispatch()}.
\begin{minted}[fontsize=\tiny]{javascript}
const action = { type: 'TOGGLE_TODO', index: 6 } // 'type' is the only thing required
\end{minted}
\textbf{Action creators} are functions that return actions
\begin{minted}[fontsize=\tiny]{javascript}
function addTodo (text) {
returns { type: 'ADD_TODO', text }
}
store.dispatch(addTodo('Pray to Yisus'))
const boundAddTodo = text => store.dispatch(addTodo(text))
boundAddTodo('Pray to Yisus')
\end{minted}
\end{frame}
\begin{frame}[fragile]
\frametitle{Reducers}
Specify how the application's state changes in response to actions.
\begin{multicols}{2}
\footnotesize State
\begin{minted}[fontsize=\tiny]{javascript}
{
visibilityFilter: 'SHOW_ALL',
todos: [
{
text: 'Consider using Redux',
completed: true,
},
{
text: 'Keep all state in a single tree',
completed: false
}
]
}
\end{minted}
\columnbreak
\footnotesize Action
\begin{minted}[fontsize=\tiny]{javascript}
{
type: 'SET_VISIBILITY_FILTER',
filter: 'SHOW_FINISHED'
}
\end{minted}
\end{multicols}
\end{frame}
\begin{frame}[fragile]
\frametitle{Reducers}
\small The reducer is a pure function \textit{(previousState, action) => newState}
\begin{minted}[fontsize=\tiny]{javascript}
function todoApp (state = initialState, action) { // initializes the state
switch (action.type) { // looks the type of the action
case SET_VISIBILITY_FILTER:
return Object.assign({}, state, { // returns the new state object
visibilityFilter: action.filter // with the changed visibility filter
})
case ADD_TODO:
return Object.assign({}, state, {
todos: [
...state.todos,
{
text: action.text,
completed: false
}
]
})
default:
return state
}
}
\end{minted}
\end{frame}
\begin{frame}[fragile]
\frametitle{Reducers composition}
\begin{multicols}{2}
\scriptsize One reducer for each part of the tree
\begin{minted}[fontsize=\tiny]{javascript}
function visibilityFilter(
state = SHOW_ALL, action
) {
switch (action.type) {
case SET_VISIBILITY_FILTER:
return action.filter
default:
return state
}
}
function todos (state = [], action) {
switch (action.type) {
case ADD_TODO:
return [
...state,
{
text: action.text,
completed: false
}
]
default:
return state
}
}
\end{minted}
\columnbreak
\scriptsize State
\begin{minted}[fontsize=\ssmall]{javascript}
{ visibilityFilter: 'SHOW_ALL',
todos: [
{ text: 'Consider using Redux',
completed: true, },
{ text: 'Keep all state in a single tree',
completed: false } ] }
\end{minted}
\scriptsize All the reducers are combined in one
\begin{minted}[fontsize=\tiny]{javascript}
function todoApp (state = {}, action) {
return {
visibilityFilter: visibilityFilter(
state.visibilityFilter, action),
todos: todos(state.todos, action)
}
}
// Redux let's us do it with combineReducers
import { combineReducers } from 'redux'
const todoApp = combineReducers({
visibilityFilter,
todos
})
\end{minted}
\end{multicols}
\end{frame}
\begin{frame}[fragile]
\frametitle{Store API}
\begin{multicols}{2}
\footnotesize Implementation
\begin{minted}[fontsize=\tiny]{javascript}
const createStore = reducer => {
let state
let listener = []
const getState = () => state
const dispatch = action => {
state = reducer(state, action)
listeners.forEach(
listener => listener()
)
}
const subscribe = listener => {
listeners.push(listener)
return () => {
listeners = listeners.filter(
l => l !== listener
)
}
}
}
\end{minted}
\columnbreak
\footnotesize Usage
\begin{minted}[fontsize=\tiny]{javascript}
import { createStore } from 'redux'
import todoApp from './reducers'
let store = createStore(todoApp)
// Every time the state changes, log it
// Note that subscribe() returns a function
// for unregistering the listener
let unsubscribe = store.subscribe(() =>
console.log(store.getState())
)
// Dispatch some actions
store.dispatch(addTodo('Learn about actions'))
store.dispatch(addTodo('Learn about reducers'))
store.dispatch(addTodo('Learn about store'))
store.dispatch(
setVisibilityFilter(
VisibilityFilters.SHOW_COMPLETED
)
)
// Stop listening to state updates
unsubscribe()
\end{minted}
\end{multicols}
\end{frame}
\begin{frame}[fragile]
\frametitle{React integration}
\begin{minted}[fontsize=\tiny]{javascript}
import { setFilter } from 'actions'
export default class ChangeFilter extends Component { // Usage <ChangeFilter store=store />
componentDidMount () {
this.unsubscribe = // The return value of subscribe is an unsubscribe method
this.props.store.subscribe( // Subscribe to store changes
() => this.forceUpdate()) // Update the component when something changes
}
componentWillUnmount () {
this.unsubscribe() // Unsubscribe from store change notifications
}
render () {
const store = this.props.store
const state = store.getState() // Read the state of the store
return (
<div>
Current filter {state.visibilityFilter} // Read a value from the store
<Button onClick={() => store.dispatch( // Dispatch and action to update the store
setFilter('SHOW_ALL') // Action creator
)} >
SHOW ALL
</Button>
</div>
)
}
}
\end{minted}
\end{frame}
\begin{frame}[fragile]
\frametitle{React integration}
\begin{multicols}{2}
\footnotesize With \textbf{react-redux}
\begin{minted}[fontsize=\tiny]{javascript}
import { setFilter } from 'actions'
import { connect } from 'react-redux'
const ChangeFilter = props => {
return (<div>
Current filter {prop.visibilityFilter}
<Button onClick={() => props.dispatchSetFilter('SHOW_ALL')} >
SHOW ALL
</Button>
</div> ) } }
}
function mapStateToProp (state, props) {
return { // This will be passed as props
visibilityFilter = state.visibilityFilter
}
}
function mapStateToDispatch (dispatch, props) {
return { // This will be passed as props
dispatchSetFilter: filter => dispatch(setFilter(filter))
}
}
export default connect (mapStateToProps, mapDispatchToProps)(ChangeFilter)
\end{minted}
\columnbreak
\begin{minted}[fontsize=\ssmall]{javascript}
// main.jsx where App includes our ChangeFilter
render(
<Provider store={store}> <App /> </Provider>,
document.getElementById('root')
)
\end{minted}
\end{multicols}
\end{frame}