As I embark on the journey of creating my very first MEAN stack application - an online cookbook, I have encountered a challenge in Angular. It seems like there is an issue between the service responsible for fetching recipe data from the API (RecipeDataService) and my "recipe detail" Component.
Whenever I try to load the detailed view of a recipe, none of the information retrieved by the service shows up. Additionally, I am confronted with the following error message in the browser's JavaScript console:
ReferenceError: RecipeDataService is not defined
at Object.onHandleError (core.js:4770)
at ZoneDelegate.webpackJsonp../node_modules/zone.js/dist/zone.js.ZoneDelegate.handleError (zone.js:392)
at ZoneDelegate.webpackJsonp../node_modules/zone.js/dist/zone.js.ZoneDelegate.hasTask (zone.js:444)
at ZoneDelegate.webpackJsonp../node_modules/zone.js/dist/zone.js.ZoneDelegate._updateTaskCount (zone.js:461)
at Zone.webpackJsonp../node_modules/zone.js/dist/zone.js.Zone._updateTaskCount (zone.js:285)
at Zone.webpackJsonp../node_modules/zone.js/dist/zone.js.Zone.runTask (zone.js:205)
at drainMicroTaskQueue (zone.js:595)
at ZoneTask.webpackJsonp../node_modules/zone.js/dist/zone.js.ZoneTask.invokeTask [as invoke] (zone.js:500)
at invokeTask (zone.js:1540)
at HTMLAnchorElement.globalZoneAwareCallback (zone.js:1566)
After some investigation, here are a few points that shed some light on the issue:
- The API endpoints are functioning properly. The two endpoints utilized by the RecipeDataService successfully retrieve a list of recipes and detailed information about a specific recipe respectively.
- The "recipe list" component can fetch a list of recipes using the recipe data service without any errors.
- The error arises only when attempting to display the fetched recipe information in the template of the "detail" Component. This means that while the RecipeDataService can be imported, listed as a provider, and its methods invoked without issues; it encounters an error when trying to render its data in the template.
Below is the TypeScript code for the RecipeDataService:
import { Injectable } from '@angular/core';
import { HttpClient } from "@angular/common/http";
@Injectable()
export class RecipeDataService {
constructor(private http : HttpClient) { }
/**
* Retrieves summary information on all Recipes from the database.
*/
getAllRecipes() {
return this.http.get('http://localhost/api/recipes');
}
/**
* Retrieves a single Recipe from the database.
*/
readRecipe(id: String) {
return this.http.get('http://localhost/api/recipes/' + id);
}
}
Here is the TypeScript code for the recipe detail component:
import { Component, OnInit } from '@angular/core';
import { Router, ActivatedRoute} from '@angular/router';
import 'rxjs/add/operator/switchMap';
import {RecipeDataService} from "../recipe-data.service";
@Component({
selector: 'recipe-detail',
templateUrl: './recipe-detail.component.html',
styleUrls: ['./recipe-detail.component.css'],
providers: [RecipeDataService]
})
export class RecipeDetailComponent implements OnInit {
private recipeId;
private recipe;
constructor(private route: ActivatedRoute,
private router: Router,
private recipeDataService: RecipeDataService) { }
ngOnInit(): void{
// Extract the Recipe ID as a parameter from the Route
this.recipeId = this.route.snapshot.paramMap.get('id');
// Fetch the Recipe using the database service
this.getRecipe();
}
private getRecipe() {
this.recipeDataService.readRecipe(this.recipeId).subscribe(
data => {this.recipe = data},
err => console.error(err));
}
navigateToRecipeList(): void {
this.router.navigateByUrl('/recipe-list');
}
}
Lastly, here is the HTML template for the Component:
<h3>{{recipeId}}<!-- No errors occur here --></h3>
<p>Name: {{recipe.name}}<!-- This line is triggering the error --></p>
...
I greatly appreciate your assistance in helping me resolve this issue.