// ✅ DO THIS - derived state
totalPrice = computed(() => {
  return this.items().reduce((sum, item) => sum + item.price, 0);
});

// ❌ DON'T - side effects in computed
badComputed = computed(() => {
  const data = this.data();
  this.logService.log(data); // Side effect - don't do this!
});

count = signal(0);

// Update with set()
count.set(5);

// Update with update()
count.update(value => value + 1);

// Update with mutate() for objects
user.update(u => ({ ...u, name: 'New Name' }));

effect(() => {
  analytics.track('cart-updated', {
    itemCount: this.items().length
  });
});

effect((onCleanup) => {
  const timer = setTimeout(() => { /* ... */ }, 300);
  onCleanup(() => clearTimeout(timer));
});

// Modern signal inputs (Angular 17+)
userId = input<string>('');
user = input.required<User>();

// Computed based on input
greeting = computed(() => `Hello, ${this.user()?.name}`);

// Convert Observable to Signal
users = toSignal(this.http.get('/api/users'), { initialValue: [] });

user = signal<User | null>(null, {
  equal: (a, b) => a?.id === b?.id
});