feat: add custom preloading strategy and preload service for on-demand loading

Author: sonusindhu

src/app/core/preloading/custom-preloading.strategy.ts

@@ -0,0 +1,30 @@
+import { PreloadingStrategy, Route } from '@angular/router';
+import { Injectable } from '@angular/core';
+import { Observable, Subject } from 'rxjs';
+import { switchMap } from 'rxjs/operators';
+
+@Injectable({ providedIn: 'root' })
+export class CustomPreloadingStrategy implements PreloadingStrategy {
+ private preloadTriggers: { [key: string]: Subject<void> } = {};
+
+ preload(route: Route, load: () => Observable<any>): Observable<any> {
+ console.log('CustomPreloadingStrategy: Checking route', route.data, route.path);
+ if (route.data && route.data['preloadOnDemand']) {
+ if (!this.preloadTriggers[route.path!]) {
+ this.preloadTriggers[route.path!] = new Subject<void>();
+ }
+ return this.preloadTriggers[route.path!].asObservable().pipe(
+ // When triggered, start loading
+ switchMap(() => load())
+ );
+ }
+ // Default: do not preload
+ return new Observable<any>();
+ }
+
+ triggerPreload(path: string) {
+ if (this.preloadTriggers[path]) {
+ this.preloadTriggers[path].next();
+ }
+ }
+}

src/app/core/preloading/preload.service.ts

@@ -0,0 +1,11 @@
+import { Injectable } from '@angular/core';
+import { CustomPreloadingStrategy } from './custom-preloading.strategy';
+
+@Injectable({ providedIn: 'root' })
+export class PreloadService {
+ constructor(private strategy: CustomPreloadingStrategy) {}
+
+ preload(path: string) {
+ this.strategy.triggerPreload(path);
+ }
+}