1. First step is creating action creator
Action name should be clear which page, which functionality, what is the action name
"[Load Courses Effect] All Courses Loaded",
"[Courses Resolver] Load All Courses"
Action
import { createAction, props } from "@ngrx/store";
import { Course } from "./model/course";
export const loadAllCourse = createAction(
"[Courses Resolver] Load All Courses"
export const allCoursesLoaded = createAction(
"[Load Courses Effect] All Courses Loaded",
props<{ courses: Course[] }>()
action types:
To make actions easy to work with, can create action types: basic it is just a improt and re-export
// actions-types.ts
import * as CoursesAction from "./cuorses.actions";
export { CoursesAction };
Effects:
Using 'createEffect', first param is a function to catch the event stream, second param is the options, can set '{dispatch: false}' which mean no other dispath event for this effect.
import { Injectable } from "@angular/core";
import { Actions, ofType } from "@ngrx/effects";
import { createEffect } from "@ngrx/effects";
import { CoursesAction } from "./actions-types";
import { CoursesHttpService } from "./services/courses-http.service";
import { concatMap, map, tap } from "rxjs/operators";
@Injectable()
export class CoursesEffects {
constructor(
private action$: Actions,
private coursesHttpService: CoursesHttpService
loadAllCourses$ = createEffect(() =>
this.action$.pipe(
ofType(CoursesAction.loadAllCourse),
concatMap(() => this.coursesHttpService.findAllCourses()),
map(courses => CoursesAction.allCoursesLoaded({ courses }))
import { Injectable } from "@angular/core";
import { Router } from "@angular/router";
import { Actions, ofType, createEffect } from "@ngrx/effects";
import { AuthActions } from "./action-types";
import { tap } from "rxjs/operators";
@Injectable()
export class AuthEffects {
constructor(private action$: Actions, private router: Router) {}
login$ = createEffect(
this.action$.pipe(
ofType(AuthActions.login),
tap(action => {
localStorage.setItem("user", JSON.stringify(action.user));
{ dispatch: false }
logout$ = createEffect(
this.action$.pipe(
ofType(AuthActions.logout),
tap(action => localStorage.removeItem("user")),
tap(() => this.router.navigateByUrl("/"))
{ dispatch: false }
Register effect:
@NgModule({
imports: [
EffectsModule.forFeature([AuthEffects])
Reducers:
Reducer mainly take care five things:
1. Define state interface
2. Creating adapter
3. Generate intialize state
4. Generate next state for one action
5. Export selector
1. Initial state:
First we need to have the interface defined for the state:
export interface CoursesState {
entities: { [key: number]: Course };
ids: number[];
NgRx provide API to create state interface:
import { EntityState, createEntityAdapter } from "@ngrx/entity";
export interface CoursesState extends EntityState<Course> {
/**Extend the entity here */
allCoursesLoaded: boolean;
'EntityState' contains 'entities' & 'ids'.
And we can extends interface by providing extra props: for example: 'allCoursesLoaded'.
2. Create Adapter:
export const adapter = createEntityAdapter<Course>({
sortComparer: compareCourses
// selectId: course => course.id // NgRx use 'id' by default
3. Generate initial state:
We can use 'adapter' to create initialstate
export const initCoursesState = adapter.getInitialState({
allCoursesLoaded: false
4. Create Reducer:
export const coursesReducer = createReducer(
initCoursesState,
on(CoursesAction.allCoursesLoaded, (state, action) =>
adapter.addAll(action.courses, { ...state, allCoursesLoaded: true }) // next state
5. Export selector:
export const { selectAll } = adapter.getSelectors();
Full code:
import { Course, compareCourses } from "../model/course";
import { EntityState, createEntityAdapter } from "@ngrx/entity";
import { createReducer, on } from "@ngrx/store";
import { CoursesAction } from "../actions-types";
export interface CoursesState {
entities: { [key: number]: Course };
ids: number[];
export interface CoursesState extends EntityState<Course> {
/**Extend the entity here */
allCoursesLoaded: boolean;
export const adapter = createEntityAdapter<Course>({
sortComparer: compareCourses
// selectId: course => course.id // NgRx use 'id' by default
export const initCoursesState = adapter.getInitialState({
allCoursesLoaded: false
export const coursesReducer = createReducer(
initCoursesState,
on(CoursesAction.allCoursesLoaded, (state, action) =>
adapter.addAll(action.courses, { ...state, allCoursesLoaded: true })
export const { selectAll } = adapter.getSelectors();
5. Selector:
Selecotor mainly has two API: createFeatureSelector & createSelector:
import { createSelector, createFeatureSelector } from "@ngrx/store";
import * as fromCourses from "./reducers/courses.reducers";
export const selectCoursesState = createFeatureSelector<
fromCourses.CoursesState
>("courses");
export const selectAllCourses = createSelector(
selectCoursesState,
fromCourses.selectAll
export const selectAllCoursesLoaded = createSelector(
selectCoursesState,
state => state.allCoursesLoaded
export const selectBeginnerCourses = createSelector(
selectAllCourses,
courses => courses.filter(course => course.category === "BEGINNER")
export const selectAdvancedCourses = createSelector(
selectAllCourses,
courses => courses.filter(course => course.category === "ADVANCED")
export const selectPromoTotal = createSelector(
selectAllCourses,
courses => courses.filter(course => course.promo).length
Component:
import { Component, OnInit } from "@angular/core";
import { compareCourses, Course } from "../model/course";
import { Observable } from "rxjs";
import { defaultDialogConfig } from "../shared/default-dialog-config";
import { EditCourseDialogComponent } from "../edit-course-dialog/edit-course-dialog.component";
import { MatDialog } from "@angular/material";
import { Store, select } from "@ngrx/store";
import { AppState } from "../../reducers";
import * as coursesSelector from "../courses.selectors";
@Component({
selector: "home",
templateUrl: "./home.component.html",
styleUrls: ["./home.component.css"]
export class HomeComponent implements OnInit {
promoTotal$: Observable<number>;
beginnerCourses$: Observable<Course[]>;
advancedCourses$: Observable<Course[]>;
constructor(private dialog: MatDialog, private store: Store<AppState>) {}
ngOnInit() {
this.reload();
reload() {
this.beginnerCourses$ = this.store.pipe(
select(coursesSelector.selectBeginnerCourses)
this.advancedCourses$ = this.store.pipe(
select(coursesSelector.selectAdvancedCourses)
this.promoTotal$ = this.store.pipe(
select(coursesSelector.selectPromoTotal)
onAddCourse() {
const dialogConfig = defaultDialogConfig();
dialogConfig.data = {
dialogTitle: "Create Course",
mode: "create"
this.dialog.open(EditCourseDialogComponent, dialogConfig);
select:
'select' operator can be used in many places, mainly if you want to get piece of data from store, for example, it can be used in resolver as well:
import { Injectable } from "@angular/core";
import {
Resolve,
ActivatedRouteSnapshot,
RouterStateSnapshot
} from "@angular/router";
import { Observable } from "rxjs";
import { Store, select } from "@ngrx/store";
import { AppState } from "../reducers";
import { CoursesAction } from "./actions-types";
import { tap, first, finalize, filter } from "rxjs/operators";
import { adapter } from "./reducers/courses.reducers";
import { selectAllCoursesLoaded } from "./courses.selectors";
@Injectable()
export class CoursesResolver implements Resolve<any> {
loading = false;
constructor(private store: Store<AppState>) {}
resolve(
route: ActivatedRouteSnapshot,
state: RouterStateSnapshot
): Observable<any> {
return this.store.pipe(
select(selectAllCoursesLoaded),
tap(courseLoaded => {
if (!this.loading && !courseLoaded) {
this.loading = true;
this.store.dispatch(CoursesAction.loadAllCourse());
// this resolve need to complete, so we can use first()
filter(courseLoaded => courseLoaded),
first(),
finalize(() => (this.loading = false))
