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Angular Resolver Tutorial

An Angular resolver is a service that helps you pre-fetch data for your components so that they can be resolved before the route is activated. In this tutorial, we'll learn how to use the Angular resolver to help us pre-fetch data for our components.

What is an Angular Resolver?

An Angular resolver is a service that helps you pre-fetch data for your component so that it can be resolved before the route is activated. This means that when a user navigates to the route that contains the component, the data for that component will be already loaded and ready to be used. This eliminates the need to manually fetch the data from the server or other sources.

Creating an Angular Resolver

To create a resolver, first create a service using the CLI:

ng generate service my-resolver

Then, add the following code to the my-resolver.service.ts file:

import { Injectable } from '@angular/core';
import { Resolve, ActivatedRouteSnapshot, RouterStateSnapshot } from '@angular/router';

@Injectable({
  providedIn: 'root'
})
export class MyResolver implements Resolve {

  constructor() { }

  resolve (
    route: ActivatedRouteSnapshot,
    state: RouterStateSnapshot
  ) {
     // Here you can fetch the data for the component
  }

}

You also need to add the MyResolver service to the routes for the component where you want to use it. For example:

const routes: Routes = [ 
  {
    path: 'my-component',
    component: MyComponent,
    resolve: {
      data: MyResolver,
    },
  }
];

Using the Resolved Data

Once the data is resolved, it can be accessed in the component's constructor by injecting the ActivatedRoute and using the get method to access the data. For example:

constructor(private route: ActivatedRoute) {
  const data = this.route.snapshot.data['data'];
  // use the data here
}

This is just a basic example of how to use an Angular Resolver. You can extend the code to include more complex scenarios such as resolving nested routes and lazy loading data.

Summary

In this tutorial, we learned how to use the Angular Resolver to pre-fetch data for our components so that they can be resolved before the route is activated. We also saw how to use the resolved data in the component's constructor. With Angular Resolvers, we can make our applications faster and more efficient.