A session I delivered in GDG Rishon about the Redux pattern and how to use it in Angular apps

1. Redux Data Flow with Angular
Gil Fink
sparXys CEO
@gilfink / www.gilfink.net

2. SPAs Are Complex

3. Service
Component
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4. Service
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Service Component
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5. Service
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Service Component
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ComponentComponent
Component
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Service Component
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ComponentComponent
Component
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Service Component
Service

6. Then you make a small change…

8. About Me
• sparXys CEO and senior consultant
• Microsoft MVP in the last 8 years
• Pro Single Page Application Development (Apress) co-author
• 4 Microsoft Official Courses (MOCs) co-author
• GDG Rishon and AngularUP co-organizer

9. Agenda
• The Redux pattern
• Combining Redux and Angular
• ng2-redux library in a nutshell

10. Known SPA Complexity Solutions
• Command Query Responsibility Segregation (CQRS)
• Event Sourcing
• Flux
• And more

11. Redux
• Design pattern based on Flux
• But it’s not Flux!
• Predictable state container for JavaScript apps

12. Redux Principles
1. Single source of truth

13. Single Source of Truth
• The application state is stored in an object tree within a single store
let state = store.getState();

14. Redux Principles
1. Single source of truth
2. State is read-only

15. State is Read-Only
• The only way to mutate the state is to emit an action describing what
happened
store.dispatch({
type: 'ADD_GROCERY_ITEM',
item: { productToBuy: 'Milk' }
});
store.dispatch({
type: 'REMOVE_GROCERY_ITEM',
index: 3
});

16. Redux Principles
1. Single source of truth
2. State is read-only
3. Changes are made with pure functions

17. Changes Are Made with Pure Functions
• To specify how the state is transformed by actions, you write a pure
function
function groceryItemReducer(state, action) {
switch (action.type) {
case 'ADD_GROCERY_ITEM':
return object.assign({}, state, {
groceryItems: [
action.item,
…state.groceryItems
]
};
default:
return state;
}
}

18. Let’s drill down

19. Redux Actors
Action
Creators
View
ReducersStore

20. Actions
• Plain JavaScript objects
• Include
• Type – action type
• Payload – the change that should occur
let action = {
type: 'ADD_GROCERY_ITEM',
item: { productToBuy: 'Milk' }
};
Action
Creators

21. Action Creators
• Functions that return actions
const ADD_GROCERY_ITEM = 'ADD_GROCERY_ITEM';
function addGroceryItem(item) {
return {
type: ADD_GROCERY_ITEM,
item: item
};
}
Action
Creators

22. Reducers
• Change the state in response to things that happened in the
application
• Pure functions
function groceryItemReducer(state, action) {
switch (action.type) {
case ADD_GROCERY_ITEM:
return object.assign({}, state, {
groceryItems: [
action.item,
…state.groceryItems
]
};
default:
return state;
}
}
Reducers

23. Store
• Only one store object
• Store data accessed through getState function
• Updates only in response to dispatching an action
import {createStore} from ‘redux’;
import {groceryItemReducer} from ‘./reducers/groceryItemReducer’;
const store = createStore(groceryItemReducer);
Store

24. Redux Data Flow
Action
Creators
View
ReducersStore
interaction (click, mouse etc.)
dispatch(action) (previous state, action)
(new state)
(current state)

25. Redux Data Flow – Cont.
Action
Creators
View
ReducersStore
interaction (click, mouse etc.)
dispatch(action) (previous state, action)
(new state)
(current state)
Outside Action
(push, Ajax callback
and etc.)

26. Redux Library API
• Redux is a small and compact library:
• createStore(reducer)
• combineReducers(reducers)
• applyMiddleware(middlewares)
• compose(functions)
• bindActionCreators(creators, dispatch)
• Store API:
• store.dispatch(action)
• store.getState()
• store.subscribe(listener)

27. Demo: Redux in action

28. Redux Middleware
• Extension point between dispatching an action and the reducer
• Middleware examples:
• Logging
• Async operations
• Routing
const middleware = store => next => action => {
// do something before dispatcher
let result = next(action);
// do something after dispatcher
return result;
}
const store = createStore(reducer, applyMiddleware(middleware));

29. Demo: Redux Middleware

30. What about Angular?

31. Angular and Redux
• Redux can be applied in Angular oriented applications
• It’s a data flow pattern
• Popular Angular & Redux libraries:
• ng2-redux
• ngrx/store

32. ng2-redux
https://github.com/angular-redux/ng2-redux
npm install --save ng2-redux

33. ng2-redux - Setup
• Add the module
• Create the store and provide it in the main module
import { NgReduxModule, NgRedux } from 'ng2-redux';
@NgModule({
imports: [ /* ... */, NgReduxModule ]
})
class AppModule {
constructor(ngRedux: NgRedux<IAppState>) {
ngRedux.provideStore(store);
}
}

34. ng2-redux - Usage
• Use the @select decorator and dispatch function:
class App {
@select() counter: Observable<number>;
constructor(private ngRedux: NgRedux<IAppState>) {}
increment() {
this.ngRedux.dispatch({ type: INCREMENT});
}
}

35. Demo: Redux + Angular

36. Questions?

37. Summary
• Redux
• Is a data flow design pattern
• Reduces complexity when building big SPAs
• Can be applied in Angular apps

38. Resources
• Redux:
https://github.com/reactjs/redux
• ng2-redux:
https://github.com/angular-redux/ng2-redux
• ngrx/store:
https://github.com/ngrx/store
• My Blog – http://www.gilfink.net
• Follow me on Twitter – @gilfink

39. Thank You!