Angular

Best Practices for Angular Component Communication – A Simple Explanation

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In an Angular app, components often need to talk to each other to share data and trigger actions. But just like in real life, good communication matters! If it's messy, your app becomes hard to manage.

So, how do Angular components communicate efficiently? Here’s a Simple Analogy.🚀

Parent to Child – “Giving Instructions” (@Input)

Think of a parent component as a manager giving instructions to a team member (child component).

How? Using the @Input decorator.

🛠 Example:

Imagine a UserListComponent (parent) sending a username to UserCardComponent (child).

// Parent Component (user-list.component.ts)<app-user-card [username]="userName"></app-user-card>// Child Component (user-card.component.ts)@Input() username: string;

Use @Input when the parent needs to pass data to the child.

Child to Parent – “Reporting Back” (@Output & EventEmitter)

Now, let’s say the team member (child) wants to report progress back to the manager (parent).

How? Using @Output and EventEmitter.

Example:

A child button component informs the parent when it’s clicked.// Child Component (button.component.ts)@Output() buttonClicked = new EventEmitter<void>();onClick() {this.buttonClicked.emit();}// Parent Component (app.component.html)<app-button (buttonClicked)="handleClick()"></app-button>

Use @Output when the child needs to notify the parent.

Sibling to Sibling – “Passing Notes” (Using a Shared Service)

Think of two sibling components as coworkers passing notes via a shared message board (a service).

How? By creating a shared service with BehaviorSubject or RxJS Observables.

Example:

A CartService allows a ProductList component to update a Cart component.

// Shared Service (cart.service.ts)@Injectable({ providedIn: 'root' })export class CartService {private cart = new BehaviorSubject<number>(0);cartCount$ = this.cart.asObservable();updateCart(count: number) {this.cart.next(count);}}// Component 1 (ProductList) updates the cartthis.cartService.updateCart(newCount);// Component 2 (CartComponent) listens for changesthis.cartService.cartCount$.subscribe(count => this.cartCount = count);

Use a shared service when unrelated components need to exchange data.