Angular Signals: A Beginner’s Guide

Are you ready to dive into the exciting world of Angular Signals? In this comprehensive guide, we’ll walk you through everything you need to know to harness the power of signals in your Angular applications. From understanding the basics techniques, you’ll be equipped with the knowledge to take your development skills to the next level.

What are Signals?
Signals are a fundamental concept in Angular that allow you to granularly track state changes within your application. They provide a flexible and efficient way to manage data and optimize rendering updates.

At their core, signals are wrappers around values that can notify interested consumers when those values change. They can contain anything from simple primitives to complex data structures.

Writable Signals:
Writable signals allow you to directly update their values. You can create them using the signal function and modify their values using the .set() or .update() operations.

const count = signal(0);
// Directly set the value of the signal
count.set(3);
// Update the value using a computation
count.update(value => value + 1);

Computed Signals:
Computed signals derive their values from other signals. They are defined using the computed function and are lazily evaluated and memoized for efficient performance.

const count = signal(0);
const doubleCount = computed(() => count() * 2);
Effects:
Effects are operations that run whenever one or more signal values change. They are useful for scenarios such as logging, synchronisation, custom DOM behaviour, or rendering to third-party libraries.

effect(() => {
  console.log(`The current count is: ${count()}`);
});

Use Cases for Effects:
While effects are not commonly needed in most applications, they can be valuable in specific situations such as logging data changes, keeping data in sync with localStorage, or implementing custom rendering logic.

Injection Context
Effects can be registered within components, directives, or services, and are automatically destroyed when their enclosing context is destroyed. You can also manually destroy effects using the EffectRef.

Advanced Topics
Advanced topics such as signal equality functions, reading without tracking dependencies, and effect cleanup functions provide additional flexibility and control over signal-based reactivity.

Creating a Simple App:
To put theory into practice, let’s create a simple Angular application that demonstrates the usage of signals. We’ll build a counter app where users can increment and decrement a counter value.

@Component({
  selector: 'app-counter',
  template: `
    <button (click)="increment()">Increment</button>
    <span>{{ count }}</span>
    <button (click)="decrement()">Decrement</button>
  `
})
export class CounterComponent {
  readonly count = signal(0);
  increment() {
    this.count.update(value => value + 1);
  }
  decrement() {
    this.count.update(value => value - 1);
  }
}

With this simple counter app, users can interact with the counter value, and Angular Signals will handle the reactivity and updates efficiently.

Conclusion:
Angular Signals offer a powerful mechanism for managing state and optimizing rendering updates in Angular applications. By understanding the fundamentals and exploring advanced techniques, you can build more responsive and efficient applications. Start experimenting with signals in your Angular projects and unlock a whole new level of development capabilities!