In this Angular 8 tutorial, we will show you step by step tutorial to call REST API in Angular 8 using HttpClient? So let’s get start to learn how to call REST API in Angular 8 using HttpClient
Creating an Angular 8 Project
Now let’s create our Angular 8 project. Open a new terminal and run the following command:
$ ng new angular-httpclient-demo
The CLI will prompt you if Would you like to add Angular routing? (y/N), type y. And Which stylesheet format would you like to use? Choose CSS and type Enter.
Next, you can serve your application locally using the following commands:
$ cd ./angular-httpclient-demo
$ ng serve
Your application will be running from http://localhost:4200.
Getting News Data
Before you can fetch the news data from NewsAPI.org which offers a free plan for open source and development projects, you first need to go the register page for getting an API key.
Adding an Angular Service
Next, let’s create a service that will take care of getting data from the news API. Open a new terminal and run the following command:
$ ng generate service api
Setting up HttpClient
Next, open the src/app/app.module.ts file then import HttpClientModule and add it to the imports array:
// [...]
import { HttpClientModule } from '@angular/common/http';
@NgModule({
declarations: [AppComponent],
entryComponents: [],
imports: [
// [...]
HttpClientModule,
],
// [...]
})
export class AppModule {}
That’s all, we are now ready to use the HttpClient in our project.
Injecting HttpClient in The Angular Service
Next, open the src/app/api.service.ts file and inject HttpClient via the service constructor:
import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
@Injectable({
providedIn: 'root'
})
export class ApiService {
constructor(private httpClient: HttpClient) { }
}
Sending GET Request for Fetching Data
Next, define an API_KEY variable which will hold your API key from the News API:
export class ApiService {
API_KEY = 'YOUR_API_KEY';
Finally, add a method that sends a GET request to an endpoint for TechCrunch news:
public getNews(){
return this.httpClient.get(`https://newsapi.org/v2/top-headlines?sources=techcrunch&apiKey=${this.API_KEY}`);
}
That’s all we need to add for the service.
How the HttpClient.get() Method Works
The HttpClient get() method is designed to send HTTP GET requests. The syntax is as follows:
get(url: string, options: {
headers?: HttpHeaders;
observe: 'response';
params?: HttpParams;
reportProgress?: boolean;
responseType?: 'json';
withCredentials?: boolean;
}): Observable<HttpResponse<Object>>;
It takes a REST API endpoint and an optional options object and returns an Observable instance.
Creating an Angular 8 Component
Now, let’s create an Angular 8 component for displaying the news data. Head back to your terminal and run the following command:
$ ng generate component news
Injecting ApiService in Your Component
Next, open the src/app/news/news.component.ts file and start by importing ApiService in your component:
import { ApiService } from '../api.service';
Next, you need to inject ApiService via the component’s constructor:
import { Component, OnInit } from '@angular/core';
import { ApiService } from '../api.service';
@Component({
selector: 'app-news',
templateUrl: './news.component.html',
styleUrls: ['./news.component.css']
})
export class NewsComponent implements OnInit {
constructor(private apiService: ApiService) { }
}
Sending the GET Request & Subscribing to The Observable
Next, define an articles variable and call the getNews() method of the API service in the ngOnInit() method of the component:
export class NewsComponent implements OnInit {
articles;
constructor(private apiService: ApiService) { }
ngOnInit() {
this.apiService.getNews().subscribe((data)=>{
console.log(data);
this.articles = data['articles'];
});
}
}
This will make sure our data is fetched once the component is loaded.
We call the getNews() method and subscribe to the returned Observable which will send a GET request to the news endpoint.
Displaying Data in The Template with NgFor
Let’s now display the news articles in our component template. Open the src/app/news.component.html file and update it as follows:
<div *ngFor="let article of articles">
<h2>{{article.title}}</h2>
<p>
{{article.description}}
</p>
<a href="{{article.url}}">Read full article</a>
</div>
Adding the Angular Component to The Router
Angular CLI 8 has automatically added routing for us, so we don’t need to set up anything besides adding the component(s) to our Router configuration. Open the src/app/app-routing.module.ts file and start by importing the news component as follows:
import { NewsComponent } from './news/news.component';
Next, add the component to the routes array:
import { NgModule } from '@angular/core';
import { Routes, RouterModule } from '@angular/router';
import { NewsComponent } from './news/news.component';
const routes: Routes = [
{path:'news', component: NewsComponent}
];
@NgModule({
imports: [RouterModule.forRoot(routes)],
exports: [RouterModule]
})
export class AppRoutingModule { }
You can now access your component from the /news path.
Conclusion
In this tutorial, we used Angular 8 to build a simple news application that retrieves data from a JSON REST API using the get() method of HttpClient. We’ve seen how to subscribe to the RxJS Observable returned by the get() method and how to use the *ngFor directive to iterate over fetched data in the template. Finally, we’ve seen how we can create an Angular 8 project using Angular CLI v8, how to generate components and services and how to configure routing for the component
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