I'm facing an issue with passing data between the course-detail component and the course-play component. I tried using a shared service and BehaviorSubject, but it didn't work as expected. Strangely, there are no errors thrown, and the data remains unchanged. The only error message I see when I open course-detail.html is "ERROR ReferenceError: course is not defined". Although the data gets passed correctly to the course-detail component through the service, I struggle with getting the data back to the service so that course-play can also utilize it. Below are the relevant files:
course.ts
export interface ICourse {
course_id: number;
title: string;
autor: string;
segments: ISegment[];
}
export interface ISegment {
segment_id: number;
unit_id: number;
unit_title: string;
name: string;
type: string;
data: string;
}course.service
import { Injectable } from '@angular/core';
import { HttpClient, HttpErrorResponse } from '@angular/common/http';
import { BehaviorSubject } from 'rxjs';
import { Observable, throwError } from 'rxjs';
import { catchError, groupBy } from 'rxjs/operators';
import { ICourse } from './course';
// Inject Data from Rails app to Angular app
@Injectable()
export class CourseService{
// JSON url to get data from
private url = 'http://localhost:3000/courses';
private courseUrl = 'http://localhost:3000/courses.json';
// Subscribe data
private courseData = new BehaviorSubject<ICourse>(null);
public courseData$ = this.courseData.asObservable();
// here we set/change value of the observable
setData(course) {
this.courseData.next(course)
}
constructor(private http: HttpClient) { }
// Handle Any Kind of Errors
private handleError(error: HttpErrorResponse) {
// A client-side or network error occured. Handle it accordingly.
if (error.error instanceof ErrorEvent) {
console.error('An error occured:', error.error.message);
}
// The backend returned an unsuccessful response code.
// The response body may contain clues as to what went wrong.
else {
console.error(
'Backend returned code ${error.status}, ' +
'body was ${error.error}');
}
// return an Observable with a user-facing error error message
return throwError(
'Something bad happend; please try again later.');
}
// Get All Courses from Rails API App
getCourses(): Observable<ICourse[]> {
const coursesUrl = `${this.url}` + '.json';
return this.http.get<ICourse[]>(coursesUrl)
.pipe(catchError(this.handleError));
}
// Get Single Course by id. will 404 if id not found
getCourse(id: number): Observable<ICourse> {
const detailUrl = `${this.url}/${id}` + '.json';
return this.http.get<ICourse>(detailUrl)
.pipe(catchError(this.handleError));
}
}course-detail.component
import { Component, OnInit, Pipe, PipeTransform } from '@angular/core';
import { ActivatedRoute, Router, Routes } from '@angular/router';
import { ICourse } from '../course';
import { CourseService } from '../course.service';
// Course-detail decorator
@Component({
selector: 'lg-course-detail',
templateUrl: './course-detail.component.html',
styleUrls: ['./course-detail.component.sass']
})
export class CourseDetailComponent implements OnInit {
course: ICourse;
errorMessage: string;
constructor(private courseService: CourseService,
private route: ActivatedRoute,
private router: Router) {
}
// On start of the life cycle
ngOnInit() {
// get the current segment id to use it on the html file
const id = +this.route.snapshot.paramMap.get('id');
this.getCourse(id);
}
// Get course detail by id
getCourse(id: number) {
this.courseService.getCourse(id).subscribe(
course => this.course = course,
error => this.errorMessage = <any>error;
this.courseService.setData(course))
}
// When we click the back button in browser
onBack(): void {
this.router.navigate(['/courses']);
}
}course-play.component
import { Component, OnInit, Input} from '@angular/core';
import { ActivatedRoute, Router, Routes, NavigationEnd } from '@angular/router';
import { MatSidenavModule } from '@angular/material/sidenav';
import { ICourse } from '../course';
import { CourseService } from '../course.service';
// Couse-play decorator
@Component({
selector: 'lg-course-play-course-play',
templateUrl: './course-play.component.html',
styleUrls: ['./course-play.component.sass']
})
export class CoursePlayComponent implements OnInit {
errorMessage: string;
courseData: ICourse;
constructor(private courseService: CourseService,
private route: ActivatedRoute,
private router: Router) {
courseService.courseData$.subscribe( courseData => this.courseData = courseData)
}
// On start of the life cycle
ngOnInit() {
// get the current segment id to use it on the html file
const id = +this.route.snapshot.paramMap.get('id');
}
// When we click the back button in browser
onBack(): void {
this.router.navigate(['/courses/:id']);
}
}