Here is the code snippet from angular.io:
{ provide: RUNNERS_UP, useFactory: runnersUpFactory(2), deps: [Hero, HeroService] }
...
export function runnersUpFactory(take: number) {
return (winner: Hero, heroService: HeroService): string => {
/* ... */
};
};
My question is why deps
property is used here? What are the general cases for using deps
?
This is a way to tell Angular dependency injections what dependencies it needs to inject to the factory function returned by
runnersUpFactory
.For services there is the
@Injectable()
class to tell DI that it needs to analyze the constructor parameter of this class (same for@Component()
,@Directive()
, and@Pipe()
), but this seems not to work for functions. Therefore they introduced thedeps
parameter.DI will look up a provider using the key
Hero
and another one usingHeroService
and then will pass them as parameters to the factory function in the same order.https://angular.io/docs/ts/latest/api/core/index/FactoryProvider-interface.html