How can I delay the loading of a lazy loaded module in Angular until certain data is resolved from an API call?

How can I preload data before loading a lazy module in Angular? I attempted using app_initializer, but it didn't work due to an existing app_initializer in AppModule. Is there a different approach to achieve this?

Answer №1

One way to improve performance is by utilizing a Resolver to preprocess your data before loading the module and navigating to a specific route only after it has been completely loaded.

An example of a resolver:

import { Injectable } from '@angular/core';
import { APIService } from './api.service';

import { Resolve } from '@angular/router';

import { ActivatedRouteSnapshot } from '@angular/router';

@Injectable()
export class APIResolver implements Resolve<any> {
constructor(private apiService: APIService) {}

 resolve(route: ActivatedRouteSnapshot) {
  return this.apiService.getItems(route.params.date);
  }
}

Implementing the resolver in your route configuration:

{
 path: 'items/:date',
 component: ItemsComponent,
 resolve: { items: APIResolver }
}

To access the resolved data in the desired component:

import { ActivatedRoute } from '@angular/router';

constructor(private route: ActivatedRoute) { }
items: any[];

ngOnInit() {
 this.items= this.route.snapshot.data.items;
}

By using a component with a resolver within a module, you ensure that the module will not initialize until all data has been resolved.

For more information on resolvers, refer to https://angular.io/api/router/Resolve

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