Angular Web Framework Services & Dependency Injection 2

Question 1

Which Angular decorator marks a class as available to the DI system as a provider?

Accepted Answer

@Injectable

Answer

@Injectable marks a class so Angular's DI system knows it can be injected and, if needed, also inject its own dependencies.

Question 2

What does the `providedIn: 'root'` option inside @Injectable do?

Accepted Answer

Creates a singleton instance available application-wide via the root injector

Answer

providedIn: 'root' registers the service with the root injector, producing a single shared instance across the entire app and enabling tree-shaking.

Question 3

How do you inject a service into an Angular component using the modern inject() function (Angular 14+)?

Accepted Answer

private service = inject(MyService);

Answer

The inject() function, called in an injection context (constructor or field initializer), retrieves the service from the current injector without constructor parameter syntax.

Question 4

What is the purpose of the `@Inject()` decorator on a constructor parameter?

Accepted Answer

It specifies an injection token when the dependency type alone is insufficient

Answer

@Inject(TOKEN) explicitly tells Angular which DI token to use for that parameter, commonly used with InjectionToken values.

Question 5

Which provider syntax uses an existing service instance to satisfy a different token?

Accepted Answer

{ provide: X, useExisting: Y }

Answer

useExisting creates an alias so that token X resolves to the same instance already registered under token Y.

Angular Web Framework Practice Test

Angular Web Framework Practice Test

Angular Web Framework Services & Dependency Injection 2