Answer:50

apps/signal/43-signal-input/src/app/user.component.ts

@@ -2,8 +2,9 @@ import { TitleCasePipe } from '@angular/common';
 import {
   ChangeDetectionStrategy,
   Component,
-  Input,
-  OnChanges,
+  computed,
+  input,
+  numberAttribute,
 } from '@angular/core';
 
 type Category = 'Youth' | 'Junior' | 'Open' | 'Senior';
@@ -18,23 +19,18 @@ const ageToCategory = (age: number): Category => {
   selector: 'app-user',
   imports: [TitleCasePipe],
   template: `
-    {{ fullName | titlecase }} plays tennis in the {{ category }} category!!
+    {{ fullName() | titlecase }} plays tennis in the {{ category() }} category!!
   `,
   host: {
     class: 'text-xl text-green-800',
   },
   changeDetection: ChangeDetectionStrategy.OnPush,
 })
-export class UserComponent implements OnChanges {
-  @Input({ required: true }) name!: string;
-  @Input() lastName?: string;
-  @Input() age?: string;
+export class UserComponent {
+  readonly name = input.required<string>();
+  readonly lastName = input<string>();
+  readonly age = input(0, { transform: numberAttribute });
 
-  fullName = '';
-  category: Category = 'Junior';
-
-  ngOnChanges(): void {
-    this.fullName = `${this.name} ${this.lastName ?? ''}`;
-    this.category = ageToCategory(Number(this.age));
-  }
+  fullName = computed<string>(() => `${this.name()} ${this.lastName() ?? ''}`);
+  category = computed<Category>(() => ageToCategory(this.age()));
 }

apps/signal/50-bug-in-effect/src/app/app.component.ts

@@ -1,8 +1,10 @@
 import {
   ChangeDetectionStrategy,
   Component,
+  computed,
   effect,
   model,
+  signal,
 } from '@angular/core';
 import { FormsModule } from '@angular/forms';
 
@@ -35,18 +37,28 @@ import { FormsModule } from '@angular/forms';
   changeDetection: ChangeDetectionStrategy.OnPush,
 })
 export class AppComponent {
-  drive = model(false);
-  ram = model(false);
-  gpu = model(false);
+  protected readonly drive = model(false);
+  protected readonly ram = model(false);
+  protected readonly gpu = model(false);
+
+  private readonly currentNoSelected = signal(0);
+
+  private readonly noOfModelsSelected = computed(
+    () =>
+      [this.drive(), this.ram(), this.gpu()].filter((model) => model).length,
+  );
+
+  private prev = this.currentNoSelected();
 
   constructor() {
-    /* 
-      Explain for your junior team mate why this bug occurs ...
-    */
     effect(() => {
-      if (this.drive() || this.ram() || this.gpu()) {
+      const valueNow = this.noOfModelsSelected();
+      const shouldFireAlert = valueNow > this.prev;
+      if (shouldFireAlert) {
         alert('Price increased!');
       }
+      this.prev = valueNow;
+      this.currentNoSelected.set(valueNow);
     });
   }
 }