feat: added lazy loading for posts (now loads when card expands)

Author: StormLx

Diff for: apps/angular/59-content-projection-defer/src/app/expandable-card.ts

@@ -1,11 +1,16 @@
-import { ChangeDetectionStrategy, Component, signal } from '@angular/core';
+import {
+  ChangeDetectionStrategy,
+  Component,
+  output,
+  signal,
+} from '@angular/core';
 
 @Component({
   selector: 'app-expandable-card',
   template: `
     <button
       class="text-fg-subtle hover:bg-button-secondary-bg-hover active:bg-button-secondary-bg-active focus:outline-button-border-highlight flex w-fit items-center gap-1 py-2 focus:outline focus:outline-2 focus:outline-offset-1"
-      (click)="isExpanded.set(!isExpanded())"
+      (click)="toggleExpansion()"
       data-cy="expandable-panel-toggle">
       @if (isExpanded()) {
         <svg
@@ -51,4 +56,11 @@ import { ChangeDetectionStrategy, Component, signal } from '@angular/core';
 })
 export class ExpandableCard {
   public isExpanded = signal(false);
+
+  expanded = output<boolean>();
+
+  toggleExpansion(): void {
+    this.isExpanded.update((isExpanded) => !isExpanded);
+    this.expanded.emit(this.isExpanded());
+  }
 }

Diff for: apps/angular/59-content-projection-defer/src/app/page-2.ts

@@ -3,6 +3,7 @@ import {
   ChangeDetectionStrategy,
   Component,
   ResourceStatus,
+  signal,
 } from '@angular/core';
 import { ExpandableCard } from './expandable-card';
 
@@ -17,7 +18,7 @@ interface Post {
   selector: 'app-page-2',
   template: `
     page2
-    <app-expandable-card>
+    <app-expandable-card (expanded)="onExpansion($event)">
       <div title>Load Post</div>
       <div>
         @if (postRessource.isLoading()) {
@@ -36,8 +37,18 @@ interface Post {
   imports: [ExpandableCard],
 })
 export class Page2 {
-  public postRessource = httpResource<Post[]>(
-    'https://jsonplaceholder.typicode.com/posts',
+  // Set this signal to true to start fetching the posts
+  private readonly $loader = signal(false);
+
+  // Fetch posts from the API
+  public postRessource = httpResource<Post[]>(() =>
+    this.$loader() ? 'https://jsonplaceholder.typicode.com/posts' : undefined,
   );
   protected readonly ResourceStatus = ResourceStatus;
+
+  onExpansion(isExpanded: boolean) {
+    if (isExpanded && !this.postRessource.hasValue()) {
+      this.$loader.set(true);
+    }
+  }
 }