How to send an http get request to Rest API server in Angular 7

How to send an http get request to Rest API server in Angular 7

In this angular 7 tutorial, we’ll learn by example how to send GET requests to REST API servers in your Angular 7 application using Httplient. We’ll also see how to use Angular services, RxJS Observables, models and the async pipe.

When we built a Front end application using javascript frameworks like Angular Js, they communicate with backend servers through RESTFUL APIs and they are based on the HTTP protocol.

Angular HttpClient uses the XMLHttpRequest, which supports by old browsers.

During this tutorial, we are going to learn with examples of how to use HttpClient for get request. HttpClient is available from the @angular/common/http package. HttpClient make HTTP GET requests using the angular get() method.

Set HttpClient in your angular application

get(url: string, options: {
headers?: HttpHeaders;
observe: ‘response’;
params?: HttpParams;
reportProgress?: boolean;
responseType?: ‘json’;
withCredentials?: boolean;
}): Observable>;

We can get the data using the get() method in two ways.

1) Subscribe to the returning Observables

2) Async pipe with the returning Observables

Subscribe to the returning Observables

Let start with an example:-

Start with importing HttpClient in your component and include HttpClient via the component’s constructor.

 import { HttpClient } from '@angular/common/http';

 constructor(private httpClient: HttpClient){}

 

Now make a function for httpclient get() method

get_posts(){
this.httpClient.get(‘https://vrsoftcoder.com/wp-json/wp/v2/posts’).subscribe((response)=>{
console.log(response);
});
}

Let show the posts on the component template. First, declare a posts array inside the class.

    private posts  = []; 

And make the changes in get_posts() method as follows:-

    get_posts(){
        this.httpClient.get('https://vrsoftcoder.com/wp-json/wp/v2/posts').subscribe((response : any[])=>{
        console.log(response);
        this.posts = response;
        });
    }

Now loop the posts array using ngFor loop of angular:-

    

    

        {{item.title}}
    

Async pipe with the returning Observables

With Async pipe we first need to create an observable by following way:-

     private postsObservable : Observable ; 

Now call the get() method and commit the result to postsObservable:

this.postsObservable = this.httpClient.get('https://vrsoftcoder.com/wp-json/wp/v2/posts');

And make changes in your component template:-

    

    

        {{item.title}}
    

Angular Services

When we used HttpClient get() method direct in our component, it is against the separations of the coding rule and coding standard. To retain coding standard we used angular services. Now we have to recreate our code to use an Angular service. In Angular service we make HTTP GET requests then Angular service returns the result back to our component.

So let’s create a new service:-

    $ ng generate service postdata 

Now we have to move to get() request code to post data service. Open the src/app/postdata.service.ts and update it as follow:-

    
    import { Injectable } from '@angular/core';
    import { HttpClient } from '@angular/common/http';

    @Injectable({
        providedIn: 'root'
    })
    export class PostdataService {
    baseUrl:string = "https://vrsoftcoder.com/wp-json/wp/v2/posts";

    constructor(private httpClient : HttpClient) {}

    get_posts(){
        return this.httpClient.get(this.baseUrl);
    }
   
    }

Now Update the src/app/app.component.ts file as follows:

    
    import { Component } from '@angular/core';
    import { Observable } from 'rxjs';

    import { PostsdataService } from './postdata.service';

    /* .... */
    @Component({
    selector: 'app-root',
    templateUrl: './app.component.html',
    styleUrls: ['./app.component.css']
    })
    export class AppComponent {    
        private posts  = []; 
       
        private postsObservable : Observable ; 

        constructor(private postdataService: PostdataService){

            this.postsObservable = this.postdataService.get_posts();

            or

            this.postdataService.get_posts().subscribe((res : any[])=>{
                this.posts = res;
            });
              
        }
    }

Creating Post Model

create a model named posts.ts in the root directory of your application and update as follows:-

export interface Posts {
        id: number;
        title: string;
        slug: string;
        content: string;
    } 

Next update your app.component.ts file as follows:-

 import { Posts } from './posts';
  
    private posts : posts[] = []; 


    private postsObservable : Observable ; 

    constructor(private postsdataService: PostsdataService){

        this.postsObservable = this.postsdataService.get_posts();

        this.postsdataService.get_posts().subscribe((res : posts[])=>{
            this.posts = res;
        });
      
    }

    

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