Expert Angular

Metadata

A class can be turned into a component by annotating it with @Component and passing the necessary metadata, such as selector, template, or templateUrl. Angular considers a class as a component only after attaching metadata to it:

Let's revisit the BookComponent class we defined earlier. Angular does not consider this class as a component unless we annotate it. TypeScript leverages the ES7 feature by providing a way to decorate a class with metadata as follows:

@Component({ 
  selector:    'book-detail', 
  templateUrl: 'app/book.component.html' 
}) 
export class BookComponent { ... } 

Here, we have decorated the BookComponent class with @Component ...