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Redux workshop
- 2. Redux 2 ● Redux is a state management tool for javascript apps. ● Allows you to share the state between components
- 3. Redux 3 Store Reducers Actions State ● It integrates nicely with React. Can use it with any other view library. It allow us to track changing data. ● It’s pretty similar to component state
- 4. Why use redux? ● When we have big complicated data for complex applications. ● Any component can pull any piece of data from the redux store.So data needs to be shared between multiple components ● Helps you write applications that behave consistently. ● Run in different environments (client, server, and native), and are easy to test ● Provides a great developer experience, such as live code editing combined with a time traveling debugger. ● Reusing the components because they no longer are dependent to get the props from their parents, they can all get their state values as props ,from a single redux store 4
- 5. Actions Reducers Store State 5 Triggers an action Create & Dispatch an Action Updates store with new state based on action type Defines
- 6. Actions & Action Creators ● Actions are kind of events. And they are just objects. ● Actions look like this: ● Instead of writing them ourselves we can wrap them inside a function that returns this action object. And this function is called Action Creators. So action creators create actions. 6
- 7. Action Creators ● Action creators (functions that return action object ) make your job easier when you need to dispatch the same action at multiple places ● One action can trigger multiple side-effects, depending on how many reducers consume that action, by checking action.type and returning a new state ● In the below example action creators dispatches a synchronous action. If you want to dispatch asynchronous actions, you need to use redux thunk 7
- 8. Middlewares ● A middleware is some code you can put between the framework receiving a request, and the framework generating a response ● People use Redux middleware for logging, crash reporting, talking to an asynchronous API, routing, and more. Examples redux-thunk, redux-logger etc. 8
- 9. Redux Thunk ● Redux thunk is a middleware, that looks at every action that passes through the system and if its a function it calls that function. 9
- 10. Redux Thunk ● With a plain basic Redux store, you can only do simple synchronous updates by dispatching an action. ● Middleware extend the store's abilities, and let you write async logic that interacts with the store. ● So with redux-thunk you can handle asynchronous actions, rather than synchronous actions. 10
- 12. Asynchronous Actions( with thunk ) 12
- 13. Redux Logger ● Display prevState,nextState and action in the console Log, everytime an action is fired. ● npm i -D redux-logger 13
- 14. Reducers ● Reducers take an initial State, create a new state based on the action.type and the update the redux store with the new state. ● It must return a new state 14
- 15. Redux Store ● Store provides a universal data storage. ● You can create redux store using createStore(). We must pass reducer as its first parameter. It takes an optional second parameter as ‘intialState’ and an optional ‘middleware’ which allows us to pass multiple middlewares like ‘thunk’, ‘redux-logger’ etc. 15
- 16. Redux Store ● We can then wrap our main component inside Provider and pass our redux store into it, so any component can access redux store. ● Any component inside Provider can also dispatch an action. 16
- 17. Connect ● Connect is a higher order component, that can take upto four parameters. All are optional. https://react-redux.js.org/api/connect#connect-parameters connect(mapStateToProps?, mapDispatchToProps?) ● mapStateToProps: is a function that gives you the store values as props for your component. It takes store’s state as param and returns an object which gets added as props for your component. 17
- 18. Connect ● mapDispatchToProps: can be a function( that returns an object ) or an object. If this parameter is not passed, then your component will receive ‘dispatch’ by default. ● Each property of the returned object should be a function, that dispatches an action ● Passing mapDispatchToProps as a function ● Passing mapDisptachToProps as Object: Here fetchPosts is a actionCreator ( function ) that we have imported, that dispatches an action. 18
- 19. Connect ● The return of connect() is a wrapper function that takes your component and returns a wrapper component with the additional props that it injects. ● However it does not change your component, it just returns a new component with props injected in it. ● https://react-redux.js.org/api/connect#connect-returns 19
- 20. When to use Connect? ● There can be two types of components: 1. Smart Component 2. Dumb Component ● Smart Components are the ones which use connect(), take the store data as props use them for themselves and then can pass it to Dumb Components down in the tree. ● You should avoid passing props to multiple level child Components as it would also make them hard to test. 20
- 21. Actions Reducers Store State 21 Triggers an action Dispatch Action ( type & payload ) Updates store with new state based on action type Action: (type & payload) prevState & Action Defines
- 22. 22 Triggers an action Dispatch Action ( type & payload ) Updates store with new state based on action type Action: (type & payload) prevState & Action Defines
- 23. Steps 23 ● Create a reducer and return state based on action type ( optional : combinereducer ) ● Create(return) an action using action creator ● Create a store and pass the reducer ( optional: add middleware ) ● Call the action creator using store.dispatch( actionCreator() ) ( If not react ) Additional steps For React, ● Wrap your component inside Provider and pass store ● Connect your React with redux : connect( mapStateToProps)( Compo ) ● Call actionCreator using this.props.dispatch( actionCreator )
- 24. Difference between Component state & Store state Component State =A component state can be changed =State is managed within a component and can only be passed as props with a top to bottom data flow - State value can change, and then render function is called.. Redux Store state -A redux store state is immutable.So reducers never changes the state but create a new state each time and updates the store -Any component can access it =Reducer updates the store with a new state when an action is dispatched. 24