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Angular 4 3 Httpclient Intercept Response

Angular 4 brought some exciting new features to the table, including the powerful HttpClientModule that enables us to make HTTP requests in a clean and efficient way. One key aspect of handling HTTP requests in Angular is intercepting responses, which can be incredibly useful for various scenarios in your application.

Intercepting responses allows you to globally handle responses from HTTP requests before they reach your application components. This can be handy for tasks like logging responses, modifying responses, or even handling errors in a centralized manner. In this article, we'll delve into how you can intercept responses using Angular's HttpClient in version 4.

To intercept responses in Angular 4 using HttpClient, we need to create a custom Angular service that implements the `HttpInterceptor` interface. This service will intercept outgoing HTTP requests and incoming HTTP responses, giving us the flexibility to transform or log the data.

Typescript

import { Injectable } from '@angular/core';
import { HttpInterceptor, HttpHandler, HttpRequest, HttpEvent, HttpResponse } from '@angular/common/http';
import { Observable } from 'rxjs';

@Injectable()
export class MyHttpInterceptor implements HttpInterceptor {

  intercept(req: HttpRequest, next: HttpHandler): Observable<HttpEvent> {
    return next.handle(req).pipe(
      map((event: HttpEvent) => {
        if (event instanceof HttpResponse) {
          console.log('Response intercepted:', event);
        }
        return event;
      })
    );
  }
}

In the code snippet above, we define a custom `MyHttpInterceptor` class that implements the `HttpInterceptor` interface. The `intercept` method is where the interception logic happens. We use the `pipe` method to intercept the response and perform our desired actions, such as logging the response to the console.

Once we have our interceptor defined, we need to provide it in the Angular module's `providers` array so that Angular can use it to intercept HTTP responses globally.

Typescript

import { NgModule } from '@angular/core';
import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http';
import { MyHttpInterceptor } from './my-http-interceptor';

@NgModule({
  imports: [
    HttpClientModule
  ],
  providers: [
    {
      provide: HTTP_INTERCEPTORS,
      useClass: MyHttpInterceptor,
      multi: true
    }
  ]
})
export class AppModule { }

In the Angular module where you import `HttpClientModule`, make sure to include your interceptor in the `providers` array using the `HTTP_INTERCEPTORS` token.

By implementing this setup, every HTTP response in your Angular application will go through your custom interceptor, allowing you to handle the responses in a centralized and consistent manner. This can be a powerful tool in maintaining the integrity and efficiency of your application when dealing with HTTP communication.

Hopefully, this guide has shed some light on how you can intercept HTTP responses in Angular 4 using the HttpClient module. With this knowledge in hand, you can take your Angular applications to the next level by implementing robust response interception logic.

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