NG Interview Set I - Services Questions

Question 1

What is the use case of services?

Answer 1

• One very common use case is providing data to components, often by fetching it from a server. Though there’s no real definition of service from Angular point of view – it could do almost anything (e.g., logging is another common use case, among many)

Question 2

How are the services injected to your application?

Answer 2

• Via Angular’s DI (Dependency Injection) mechanism

Question 3

Why is it a bad idea to create a new service in a component like the one below?

let service = new DataService();

Answer 3

• The object may not be created with its needed dependencies

Question 4

How to make sure that a single instance of a service will be used in an entire application?

Answer 4

• Provide it in the root module

Question 5

Why do we need provider aliases? And how do you create one?

Answer 5

• To substitute an alternative implementation for a provider. Can create like so:

{ provide: LoggerService, useClass: DateLoggerService }