feat(challenge 59): added lazy loading for posts

Author: kevinagus

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)="expandedChange()"
       data-cy="expandable-panel-toggle">
       @if (isExpanded()) {
         <svg
@@ -51,4 +56,10 @@ import { ChangeDetectionStrategy, Component, signal } from '@angular/core';
 })
 export class ExpandableCard {
   public isExpanded = signal(false);
+  expanded = output<boolean>();
+
+  expandedChange = () => {
+    this.isExpanded.set(!this.isExpanded());
+    this.expanded.emit(this.isExpanded());
+  };
 }

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';
 
@@ -17,16 +18,18 @@ interface Post {
   selector: 'app-page-2',
   template: `
     page2
-    <app-expandable-card>
+    <app-expandable-card (expanded)="triggerFetch.set($event)">
       <div title>Load Post</div>
       <div>
-        @if (postRessource.isLoading()) {
-          Loading...
-        } @else if (postRessource.status() === ResourceStatus.Error) {
-          Error...
-        } @else {
-          @for (post of postRessource.value(); track post.id) {
-            <div>{{ post.title }}</div>
+        @if (postRessource) {
+          @if (postRessource.isLoading()) {
+            Loading...
+          } @else if (postRessource.status() === ResourceStatus.Error) {
+            Error...
+          } @else {
+            @for (post of postRessource.value(); track post.id) {
+              <div>{{ post.title }}</div>
+            }
           }
         }
       </div>
@@ -36,8 +39,11 @@ interface Post {
   imports: [ExpandableCard],
 })
 export class Page2 {
-  public postRessource = httpResource<Post[]>(
-    'https://jsonplaceholder.typicode.com/posts',
+  protected triggerFetch = signal(false);
+  public postRessource = httpResource<Post[]>(() =>
+    !this.triggerFetch()
+      ? undefined
+      : 'https://jsonplaceholder.typicode.com/posts',
   );
   protected readonly ResourceStatus = ResourceStatus;
 }