Ngrx slides

NGRXNGRX
THERE IS A REDUCER IN MY SOUPTHERE IS A REDUCER IN MY SOUP
1

About me
Google Developer Expert
Telerik Developer Expert
Digital McKinsey
@chris_noring
2

NGRX IS:NGRX IS:
An Angular implementation of Redux
3 . 1

Why do we care about Redux?
If you experience the following symtoms you might
need Redux:
A feeling that the state is spread out
There are issues with updating state
Some things keep changing the state but you don't
know who or what
Un an explainable itch
3 . 2

Solution: a single source of truth with reducers
guarding state change. Also enhanced predictability
with immutable data structures
3 . 3

CORE CONCEPTSCORE CONCEPTS
3 . 4

Store, our data store
Reducer, a function that takes state + action and
produces a new state
Selector, selects a slice of state
Action, an intention of state change
Action creator, produces an intention that may
include data
3 . 5

Typical Store content, just an object
{
counter: 'a value',
jedis: [{ id: 1, name: 'Yoda' }],
selectedJedi: { id: 1, name: 'Yoda' }
}
3 . 6

REDUCERREDUCER
NEW STATE = STATE + ACTIONNEW STATE = STATE + ACTION
3 . 7

Let's take some reducing examples:
BANANA + MILK + ICE CREAM =BANANA + MILK + ICE CREAM =
MILKSHAKEMILKSHAKE
PIZZA + HAMBURGER + ICECREAM =PIZZA + HAMBURGER + ICECREAM =
STOMACH ACHESTOMACH ACHE
3 . 8

Mathematical function, immutable, just a calculation
Immutable = Predictability
//mutating
var sum = 3;
function add(a) { sum += a; return sum; }
add(5); // 8
add(5); // 13
// immutable
function computeSum(a,b) { return a + b; }
computeSum(1,1); // 2
computeSum(1,1); // 2
3 . 9

A reducer looks like the following:
function reducer(state, action) { /* implementation */ }
state, previous/initial state
action = {
type: 'my intent, e.g ADD_ITEM',
payload: { /* some kind of object */ }
}
3 . 10

state + 1, instead of state +=1, immutable
function counterReducer(state = 0, action) {
switch(action.type) {
case 'INCREMENT':
return state + 1;
default:
return state;
}
}
3 . 11

Usage
let initialState = 0;
let state = counterReducer(initialState,{ type: 'INCREMENT' })
// 1
state = counterReducer(state, { type: 'INCREMENT' })
// 2
function counterReducer(state = 0, action) {
case 'INCREMENT':
return state + 1;
default:
return state;
}
}
3 . 12

A list reducer
function jediReducer(state = [], action) {
case 'ADD_JEDI':
return [ ...state, action.payload];
case 'REMOVE_JEDI':
return state.filter(
jedi => jedi.id !== action.payload.id);
default:
return state;
}
}
3 . 13

Usage, list reducer
let state = jediReducer([], {
type: 'ADD_JEDI',
payload: { id: 1, name: 'Yoda' }
});
// [{ id: 1, name: 'Yoda' }]
state = jediReducer(state, {
type: 'REMOVE_JEDI',
payload: { id: 1 }
});
// []
3 . 14

An object reducer
Build a new object based on old + change with
...spread
let initialState = {
loading: false,
data: [],
error: void 0
};
function productsReducer(state = initialState, action) {
case 'FETCHING_PRODUCTS':
return { ...state, loading: true };
case 'FETCHED_PRODUCTS':
return { ...state, data: action.payload, loading: false
case 'FETCHED_PRODUCTS_ERROR':
return { ...state, error: action.payload, loading: false
}
}
3 . 15

Object reducer, usage
Handling an AJAX case, can show spinner when,
loading = true
let state = productsReducer(initialState, {
type: 'FETCHING_PRODUCTS'
});
try {
let products = await getProducts(); // from an endpoint;
state = productsReducer(state, {
type: 'FETCHED_PRODUCTS',
payload: products
});
} catch (error) {
state = productsReducer(state, {
type: 'FETCHED_PRODUCTS_ERROR',
payload: error
});
}
3 . 16

A simple store
class Store {
constructor(initialState) { this.state = initialState; }
dispatch(action) {
this.state = calc(this.state, action);
}
calc(state, action) {
return {
counter: counterReducer(state.counter, action),
jedis: jediReducer(state.jedis, action)
}
}
}
3 . 17

Usage, store
let store = new Store({ counter: 0, jedis: [] });
store.dispatch({ type: 'INCREMENT' });
// { counter: 1, jedis: [] }
store.dispatch({
type: 'ADD_JEDI',
payload: { id: 1, name: 'Yoda' }
});
// { counter: 1, jedis: [{ id: 1, name: 'Yoda' }] }
store.dispatch({
type: 'REMOVE_JEDI',
payload: { id: 1 }
});
// { counter: 1, jedis: [] }
3 . 18

Action, an object with a property 'type' and 'payload'
'type' = intent
'payload' = the change
{ type: 'ADD_JEDI', payload: { id: 1, name: 'Yoda' } }
3 . 19

Action creator, function that creates action
const addJedi = (id, name) =>
({ type: 'ADD_JEDI', payload: { id, name } });
addJedi(1, 'Yoda');
// { type:'ADD_JEDI', payload: { id: 1, name: 'Yoda' } }
//usage
store.dispatch(addJedi(1, 'Yoda'));
3 . 20

Selector, slice of state
class Store {
constructor(initialState) { ... }
dispatch(action) { ... }
calc(state, action) { ... }
select(fn) {
return fn(state);
}
}
3 . 21

Selector, definitions
const getCounter = (state) => state.counter;
const getJedis = (state) => state.jedis;
3 . 22

NGRXNGRX
OVERVIEW OF LIBRARIESOVERVIEW OF LIBRARIES
4 . 1

@ngrx/store, the store
@ngrx/store-devtools, a debug tool that helps you
track dispatched actions
@ngrx/router-store, lets you put the routing state in
the store
@ngrx/eﬀects, handles side eﬀects
@ngrx/entites, handles records
@ngrx/schematics
4 . 2

STORESTORE
WHERE THE STATE LIVESWHERE THE STATE LIVES
5 . 1

INSTALLATION AND SET UPINSTALLATION AND SET UP
npm install @ngrx/store --save
// file 'app.module.ts'
import { StoreModule } from '@ngrx/store';
import { counterReducer } from './counter.reducer';
@NgModule({
imports: {
StoreModule.forRoot({
counter: counterReducer
})
}
})
export class AppModule {}
5 . 2

SHOW DATA FROM STORESHOW DATA FROM STORE
// app-state.ts
export interface AppState {
counter: number;
}
// some.component.ts
@Component({
template: ` {{ counter$ | async }} `
})
export class SomeComponent {
counter$;
constructor(this store:Store<AppState>) {
this.counter$ = this.store.select('counter');
}
}
5 . 3

SHOW DATA FROM STORE, SELECTORSHOW DATA FROM STORE, SELECTOR
FUNCTIONFUNCTION
// app-state.ts
export interface AppState {
counter: number;
}
// some.component.ts
@Component({
template: ` {{ counter$ | async }} `
})
counter$;
this.counter$ = this.store
.select( state => state.counter);
}
}
5 . 4

DISPATCH DATADISPATCH DATA
@Component({
template: `
{{ counter$ | async }}
<button (click)="increment()">Increment</button>
<button (click)="decrement()">Decrement</button>
`
})
counter$;
this.counter$ = this.store.select('counter');
}
increment() { this.store.dispatch({ type: 'INCREMENT' }); }
decrement() { this.store.dispatch({ type: 'DECREMENT' }); }
}
5 . 5

DISPATCH DATA, WITH PAYLOAD,DISPATCH DATA, WITH PAYLOAD,
TEMPLATETEMPLATE
@Component({
template: `
<input [(ngModel)]="newProduct" />
<div *ngFor="let product of products$ | async">
{{ product.name }}
<button (click)="remove(product.id)">Remove</button>
</div>
<button (click)="add()">Add</button>
`
})
5 . 6

CLASS BODYCLASS BODY
products$, id = 0;
this.counter$ = this.store.select('products');
}
remove(id) { this.state.dispatch({
type: 'REMOVE_PRODUCT', payload: { id } })
}
add() {
this.state.dispatch({
type: 'ADD_PRODUCT',
payload: { id : this.id++, this.name: newProduct }
})
}
}
5 . 7

When our app grows, we can't have all the state in
StoreModule.forRoot({})
Solution is using StoreModule.forFeature()
Let's also find a way to organize files
5 . 8

Set up store in a feature module,
StoreModule.forFeature('feature',{})
interface CombinedState {
list: Product[];
item: Product;
};
const combinedReducers: ActionReducerMap<CombinedState> = {
list: listReducer,
item: itemReducer
};
@NgModule({
imports: [
StoreModule.forFeature<CombinedState, Action>(
'products',
combinedReducers
)]
});
5 . 9

Organizing your files, Domain approach
/feature
feature.component.ts
feature.selector.ts
feature.actions.ts
feature.reducer.ts
5 . 10

Organizing your files, Ruby on Rails approach
/feature
feature.component.ts
/feature2
feature2.component.ts
/reducers
feature.reducer.ts
feature2.reducer.ts
index.ts
/selectors
feature.selector.ts
feature2.selector.ts
index.ts
/actions
feature.actions.ts
feature2.actions.ts
5 . 11

Whatever approach you go for, consistency is key
5 . 12

STORE DEVTOOLSSTORE DEVTOOLS
DEBUG LIKE A PRODEBUG LIKE A PRO
6 . 1

Install lib on NPM and download chrome extension on
http://extension.remotedev.io/
6 . 2

npm install @ngrx/store-devtools
import { StoreDevtoolsModule } from '@ngrx/store-devtools';
@NgModule({
imports: [
StoreDevtoolsModule.instrument({
maxAge: 25 // Retains last 25 states
}
)]
})
6 . 3

What can we do with it?
See dispatched actions
Undo dispatched actions
Use time travel debugging and move through time,
back and forth with a gauge
6 . 4

Initial view, we see actions as well as diﬀerent tabs
6 . 5

Here we can see the detail of an action, what type etc.
6 . 6

It records all of our actions, here multiple dispatched
actions
6 . 7

Here we are undoing/skipping an action, store is
recalculated
6 . 8

This gauge enables us to travel through time, back and
forth
6 . 9

ROUTER STOREROUTER STORE
ENABLING US TO PUT THE ROUTERENABLING US TO PUT THE ROUTER
STATE IN THE STORESTATE IN THE STORE
7 . 1

We want to accomplish the following:
Save the route state to our store
Customize whats gets saved
down
7 . 2

npm install @ngrx/router-store
import { StoreRouterConnectingModule } from '@ngrx/router-stor
@NgModule({
imports: [
StoreModule.forRoot({
router: routerReducer // this is where our route state g
}),
StoreRouterConnectingModule.forRoot({
stateKey: 'router' // name of reducer key
})
]
})
7 . 3

We can listen to this 'router' state like any other state
@Component({
template: ``
})
constructor(private state: State<AppState>) {
// updates every time we route
this.state.select('router')
.subscribe(data => console.log(data));
}
}
7 . 4

Might be a bit hard to read
7 . 5

LET'S BUILD OUR OWN ROUTER STATELET'S BUILD OUR OWN ROUTER STATE
7 . 6

The following is of interest:
The url
The router
parameters
The query parameters
7 . 7

Define a serializer, that saves url, queryParams and
router params
interface MyState {
url: string;
queryParams;
params;
}
export class MySerializer implements
RouterStateSerializer<MyState> {
serialize(routerState: RouterStateSnapshot): MyState {
console.log('serializer');
console.log('complete router state', routerState);
const { url, root: { queryParams, firstChild: { params } }
return { url, queryParams, params };
}
}
7 . 8

Provide this as the 'new' serializer
@NgModule({
providers: [{
provide: RouterStateSerializer,
useClass: MySerializer
}]
})
7 . 9

This is what the router state looks like now, only saves
exactly what we want
7 . 10

EFFECTSEFFECTS
HANDLING SIDE EFFECTSHANDLING SIDE EFFECTS
8 . 1

Objective: We want to ensure we can carry out things
like accessing resources over the network.
8 . 2

INSTALLATION AND SETUPINSTALLATION AND SETUP
npm install @ngrx/effects
import { EffectsModule } from '@ngrx/effects';
@NgModule({
EffectsModule.forRoot([ ... my effects classes ])
})
8 . 3

What kind of behaviour do we want?
Set a loading flag, show spinner
Do AJAX call
Show fetched data or error
Set loading flag to false, hide
spinner
8 . 4

NGRX approach
try {
store.dispatch({ type: 'FETCHING_DATA' })
// state: { loading: true }
const data = await getData(); // async operation
store.dispatch({ type: 'FETCHED_DATA', payload: data });
// state: { loading: false, data: {/* data from endpoint */}
} catch (error) {
store.dispatch({
type: 'FETCHED_DATA_ERROR',
payload: error
});
}
8 . 5

My first eﬀect
@Injectable()
export class ProductEffects {
@Effect()
products$: Observable<Action> = this.actions$.pipe(
ofType(FETCHING_PRODUCTS),
switchMap(
// ensure we dispatch an action the last thing we do
action => of({ type: "SOME_ACTION" })
)
);
constructor(private actions$: Actions<Action>, private http:
console.log("product effects init");
}
}
8 . 6

My first eﬀect - calling HTTP
@Injectable()
export class ProductEffects {
@Effect()
products$: Observable<Action> = this.actions$.pipe(
ofType(FETCHING_PRODUCTS), // listen to this action
switchMap(action =>
this.http
.get("data/products.json")
.pipe(
delay(3000),
map(fetchProductsSuccessfully), // success
catchError(err => of(fetchError(err))) // error
)
)
);
8 . 7

ENTITESENTITES
REDUCE THAT BORING BOILER PLATEREDUCE THAT BORING BOILER PLATE
9 . 1

Install and set up
npm install @ngrx/entity
import {
EntityState,
createEntityAdapter,
EntityAdapter } from "@ngrx/entity";
// set up the adapter
const adapter: EntityAdapter<User> =
createEntityAdapter<User>();
// set up initial state
const initial = adapter.getInitialState({
ids: [],
entities: {}
});
9 . 2

Install and set up
/*
use the adapter methods
for specific cases like adapter.addOne()
*/
function userReducer(
state = initial,
action: ActionPayload<User>
) {
switch (action.type) {
case "ADD_USER":
return adapter.addOne(action.payload, state);
default:
return state;
}
}
9 . 3

What else can it do for us?
addOne: Add one entity to the collection
addMany: Add multiple entities to the collection
addAll: Replace current collection with provided
collection
removeOne: Remove one entity from the collection
removeMany: Remove multiple entities from the
collection
removeAll: Clear entity collection
updateOne: Update one entity in the collection
updateMany: Update multiple entities in the
collection 9 . 4

Further reading:
https://github.com/ngrx/platform/tree/master/docs/ent
9 . 5

SCHEMATICSSCHEMATICS
BE LAZY AND SCAFFOLD :)BE LAZY AND SCAFFOLD :)
10 . 1

It is a scaﬀolding library that helps us scaﬀold out
NGRX features
10 . 2

Schematics can help us scaﬀold the following:
Action
Container
Eﬀect
Entity
Feature
Reducer
Store
10 . 3

Install and set up
// install schematics and prerequisits
npm install @ngrx/schematics --save-dev
npm install @ngrx/{store,effects,entity,store-devtools} --save
// we might need this one as well
npm install --save @angular/cli@latest
10 . 4

Scaﬀold, initial state set up, forRoot({}) and
instrument()
ng generate store State --root --module app.module.ts --collec
// result
@NgModule({
declarations: [ ... ],
imports: [
BrowserModule,
StoreModule.forRoot(reducers, { metaReducers }),
!environment.production ? StoreDevtoolsModule.instrument()
],
bootstrap: [AppComponent]
})
export class AppModule { }
10 . 5

Scaﬀold, setting up eﬀects for the App
ng generate effect App --root --module app.module.ts --collect
@NgModule({
declarations: [
AppComponent
],
imports: [
...
EffectsModule.forRoot([AppEffects])
],
providers: [],
bootstrap: [ ... ]
})
export class AppModule { }
10 . 6

Scaﬀold, create Action, generates action and test
ng generate action User --spec
export enum UserActionTypes {
UserAction = '[User] Action'
}
export class User implements Action {
readonly type = UserActionTypes.UserAction;
}
export type UserActions = User;
10 . 7

Scaﬀold, create a component, with store injected
ng generate container TodoList
@Component({
selector: 'app-todo-list',
templateUrl: './todo-list.component.html',
styleUrls: ['./todo-list.component.css']
})
export class TodoListComponent implements OnInit {
constructor(private store: Store<any>) { }
ngOnInit() {
}
}
10 . 8

DO IT YOURSELFDO IT YOURSELF
BUILD YOUR OWN NGRXBUILD YOUR OWN NGRX
11 . 1

What requirements do we have?
Should be possible to dispatch actions
State should update when we dispatch
It should be possible to subscribe to a slice of
state
We should support side eﬀects
11 . 2

BEHAVIOURSUBJECTBEHAVIOURSUBJECT
SUPPORTS A STATE, CAN BESUPPORTS A STATE, CAN BE
SUBSCRIBED TOSUBSCRIBED TO
11 . 3

BehaviorSubject
// ctor value = inital value
let subject = new BehaviorSubject({ value: 1 })
subject.subscribe(data => console.log('data', data));
// { value: 1 }
// { prop: 2}
subject.next({ prop: 2 });
11 . 4

Merging states with .scan()
let subject = new BehaviorSubject({ value: 1 }) // {} inital
subject
.scan((acc, value) =>({ ...acc, ...value }))
.subscribe(data => console.log('data', data));
subject.next({ prop: 2 }); // { value: 1, prop: 2 }
11 . 5

Implementing the store
class Store extends BehaviorSubject {
constructor(initialState = {}) {
super(initialState);
this.listenerMap = {};
this.dispatcher = new Subject();
this.dispatcher
.scan((acc, value) =>({ ...acc, ...value }))
.subscribe(state => super.next(state));
}
dispatch(newState) {
this.dispatcher.next(newState);
}
}
11 . 6

Usage, store
store = new Store();
store.subscribe(data => console.log('state', data));
store.dispatch({ val: 1 });
store.dispatch({ prop: 'string' });
// { val: 1, prop: 'string' }
11 . 7

What about slice of state?
class Store extends BehaviorSubject {
constructor(initialState = {}) {
...
}
dispatch(newState) {
}
select(slice) { return this.map[slice] }
selectWithFn(fn) { return this.map(fn) }
}
11 . 8

We need to improve the core implementation, enter
storeCalc()
const storeCalc = (state, action) => {
return {
counter: countReducer(state.counter, action),
products: productsReducer(state.products, action)
}
};
11 . 9

A retake on our dispatch(), old state, getValue() +
action = new state
dispatch(action) {
const newState = storeCalc(this.getValue(),action);
}
11 . 10

LETS' TALK ABOUT EFFECTSLETS' TALK ABOUT EFFECTS
11 . 11

We need to be able to signup to specific
actions
We need to be able to carry out side eﬀects
11 . 12

First let's set up subscription in the store
class Store {
constructor() { ... }
dispatch() { ... }
select() { ... }
effect(listenToAction, listener) {
if(!this.listenerMap.hasOwnProperty(listenToAction)) {
this.listenerMap[listenToAction] = [];
}
this.listenerMap[listenToAction].push( listener );
}
}
11 . 13

Then ensure the eﬀect happens in dispatch()
class Store {
constructor() { ... }
dispatch() {
const newState = storeCalc(this.getValue(),action);
// tell our listeners this action.type happened
if(this.listenerMap[action.type]) {
this.listenerMap[action.type].forEach(listener => {
listener(this.dispatch.bind(this),action);
});
}
}
select() { ... }
effect(listenToAction, listener) { ... }
}
11 . 14

use our new eﬀect() method
let store = new Store();
store.effect('INCREMENT' ,async(dispatch, action) => {
// side effect
let products = await getProducts();
// side effect
let data = await getData();
// dispatch, if we want
dispatch({ type: 'INCREMENT' });
})
store.dispatch({ type: 'DECREMENT' });
11 . 15

We learned how to:
Grasp the basics of Redux
NGRX building blocks
Use the store
Leverage the dev tools and its Redux plugin
Store our router state and transform it
How we handle side eﬀect like AJAX calls
Remove boiler plate with Entity
How to be even lazier with the scaﬀold tool
Schematics
Upgrading ourselves to Ninja level by learning how
to implement NGRX
12 . 2

Further reading:
Free video course,
https://platform.ultimateangular.com/courses/ngrx-st
eﬀects
Redux docs, https://redux.js.org/docs
Probably the best homepage on it, Brian Troncone,
https://gist.github.com/btroncone/a6e4347326749f93
12 . 3

Buy my book ( please :) ):
https://www.packtpub.com/web-
development/architecting-angular-applications-flux-
redux-ngrx
12 . 4

Thank you for listening
12 . 5

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