Angular 17 resolvers

Angular 17 resolvers

Angular resolvers have long been recognized as a potent tool to elevate the performance and dependability of your applications. They enable you to fetch data in advance of rendering a component, ultimately enhancing the user experience and mitigating potential errors.

In Angular 17, resolvers have undergone significant improvements, making them even more versatile and valuable:

  • Data Resolution for Any Route Type: In Angular 17, resolvers can resolve data not just for route parameters but for a wide range of route types, including child routes and query parameters. This versatility empowers you to pre-fetch data efficiently for various parts of your application.

  • Introduction of resolve() Method: Angular 17 introduces the resolve() method, allowing you to resolve data for multiple routes concurrently. This capability proves beneficial when you need to load multiple pieces of data for a single component.

  • Custom Resolver Creation with ResolverFactory: Angular 17 presents the ResolverFactory service, enabling you to craft custom resolvers. This affords greater control over the data resolution process and allows you to tailor resolvers to the specific requirements of your application.

Let's delve into an example of a straightforward resolver designed to resolve data for a single route:

import { Injectable } from '@angular/core';
import { Resolve, ActivatedRouteSnapshot, RouterStateSnapshot } from '@angular/router';
import { Observable } from 'rxjs';
import { Post } from './post';

  providedIn: 'root'
export class PostResolver implements Resolve<Post> {

  constructor(private postService: PostService) {}

  resolve(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Observable<Post> {
    const postId = route.params['id'];
    return this.postService.getPostById(postId);

In this example, the resolver retrieves a post by its ID from a service. Subsequently, the resolver is registered with the Angular application in the root module.

  declarations: [
    // Component declarations
  imports: [
    // Module imports
  providers: [
  bootstrap: [AppComponent]
export class AppModule { }

The resolver is then employed in the routing configuration for the post detail component:

import { RouterModule, Routes } from '@angular/router';

const routes: Routes = [
  { path: '', redirectTo: '/posts', pathMatch: 'full' },
  { path: 'posts', component: PostListComponent },
  { path: 'posts/:id', component: PostDetailComponent, resolve: { post: PostResolver } }

Now, when a user navigates to the post detail component, Angular invokes the resolve() method of the PostResolver before rendering the component. Subsequently, the resolver retrieves the post by its ID and passes it to the component's ngOnInit() method.

Benefits of Using Resolvers in Angular 17:

  • Enhanced Performance: Resolvers boost application performance by pre-fetching data before it's needed, reducing component rendering time, and elevating the overall user experience.

  • Reduced Boilerplate Code: Resolvers streamline data fetching by providing a centralized data acquisition location, resulting in more maintainable and comprehensible code.

  • Improved Data Consistency: Resolvers ensure that components consistently have the necessary data upon rendering, helping to avert errors and enhance overall application quality.


In conclusion, Angular resolvers are a formidable asset for improving both the performance and reliability of your applications. They offer advanced data resolution capabilities and contribute to code maintainability, ultimately enhancing the quality of your Angular projects.