Enhance Your Angular App with Route Resolvers
Published: 2023-06-23 19:20:01

## Enhance Your Angular App with Route Resolvers



Angular is a popular web development framework used to build dynamic front-end applications. One of the key features of Angular is its powerful routing module. Angular’s routing module enables developers to build single-page applications with a seamless user experience by enabling navigation between different views, while also maintaining the state of the application.

 

However, when a user navigates to a new route, there can be a delay in loading data from the server, which can lead to a poor user experience. Fortunately, Angular provides a solution to this problem: Route Resolvers.



### What are Route Resolvers?



Route resolvers in Angular are services that execute code to fetch data before navigating to a new route. They are used to prefetch data before navigating to a new route and to ensure the component receives the data it needs when it’s loaded. Route resolvers allow you to resolve data and then navigate to the new route only when the resolved data is available. They can be used at any level of the route configuration to resolve data before activation of a route or child route, including the application-wide level, route level, and sub-tree level.



### An Example Use Case Of Route Resolvers



Let's say we are working on an aviation application and want to display data for a specific aircraft on the ‘/aircraft’ route in our Angular app. To get the aircraft data, the application will need to make an API call to fetch the data from the server. 



We could simply load the component for our aircraft route and then retrieve the aircraft data in the component, but this approach can cause a delay in rendering the component and affect the user experience. A better solution is to use route resolvers to fetch the aircraft data before activating the route. 



We can achieve this by implementing a resolver service in our app that retrieves aircraft data from the server. Here’s an example:



<pre><code>
import { Injectable } from '@angular/core';
import { Resolve } from '@angular/router';
import { Observable } from 'rxjs';
import { Aircraft } from './aircraft.model';
import { AircraftService } from './aircraft.service';

@Injectable()
export class AircraftResolverService implements Resolve&lt;Aircraft&gt; {
  constructor(private aircraftService: AircraftService){}

  resolve(): Observable&lt;Aircraft&gt; {
    return this.aircraftService.getAircraftData();
  }
}
</code></pre>

In the route configuration, we can then define that the AircraftResolverService should be used to pre-fetch the data before navigating to the aircraft route:



<pre><code>
const routes: Routes = [
  {
    path: 'aircraft',
    component: AircraftComponent,
    resolve: {
      aircraft: AircraftResolverService
    }
  }
];
</code></pre>

In the route configuration above, we have defined that the ‘aircraft’ route should activate the ‘AircraftComponent’ component and call the AircraftResolverService to pre-fetch the data. The ‘aircraft’ route can only be activated once the AircraftResolverService has resolved the data.



In the ‘AircraftComponent’, we can then retrieve the pre-fetched data by injecting the resolver data into our component using Angular’s ActivatedRoute service:



<pre><code>
import { Component, OnInit } from '@angular/core';
import { ActivatedRoute } from '@angular/router';
import { Aircraft } from './aircraft.model';

@Component({
  selector: 'app-aircraft',
  templateUrl: './aircraft.component.html',
  styleUrls: ['./aircraft.component.css']
})
export class AircraftComponent implements OnInit {
  aircraft: Aircraft;

  constructor(private route: ActivatedRoute) { }

  ngOnInit() {
    this.route.data.subscribe(data => this.aircraft = data['aircraft']);
  }
}
</code></pre>

In the code above, we inject the ‘ActivatedRoute’ service into our component and retrieve the pre-fetched aircraft data using the ‘data’ property resolved by our resolver service.



### Benefits of Route Resolvers



The benefits of using route resolvers in Angular are clear. Firstly, they allow you to pre-fetch data before navigating, ensuring that the component loads with minimal delay, and offering a better user experience. Secondly, they make it easier to manage data, as you can pass data to the component as part of the resolver result.



Lastly, route resolvers can be extended to allow developers to add more logic to the data fetching process. They allow developers to execute custom code to fetch data in a particular way, and to transform or manipulate the data before passing it on to the component. This can enable developers to better manage the data being used in their applications, including the ability to handle errors and exceptions.



### Conclusion



In conclusion, route resolvers are an important feature of the Angular framework, and offer a simple and intuitive way to resolve data before navigating to a new route. By pre-fetching data, route resolvers can offer a better user experience by ensuring that components load quickly, and the application maintains a seamless flow. Additionally, route resolvers enable developers to better manage data in their applications, with the ability to execute custom code and manipulate the retrieved data before passing it on to the component.



Beyond this use case of aircraft data in aviation application, route resolvers can be applied in various domains to enhance the performance and user experience of Angular applications.