angular interface style guide - unclear recommendations

Question

I've read the Angular style guide for interfaces , and there are two recommendations there that are completely unclear to me:

Consider using a class instead of an interface for services and declarables (components, directives, and pipes).

Consider using an interface for data models.

Why? A class can act as an interface (use implements instead of extends).

Why? An interface-class can be a provider lookup token in Angular dependency injection.

In the first case, is there even an alternative to defining a service as a class?

In the second case, the recommendation seems contrary to Angular's Tour of Heroes tutorial (has it been updated lately?), where the Hero model is defined as a class, like so:

export class Hero {
  constructor(public id: number, public name: string) { }
}

And also, what is an interface-class and what does it mean a provider lookup token ?

I think that several examples could really clarify things here.

Thanks.

Answer 1

1. This is a little out of context but what they are referring to is using a class (model) for retrieving data ie this.service.getSomething().subscribe((model: myModel) => model); .

2. An interface-class is a class that acts as an interface aka a model.

3. A provider lookup token is how angular knows what provider to use. There is a more in-depth explanation here .