Angular2 - inject into @Injectable

Question

I have an Angular2 app with a service that is used for getting a data from an API. Following this example, I want to create a separate file which s

Answer 1

It is a bit strange, but only components can configure dependency injection in Angular (well, and bootstrap(), but that is essentially the same as the root component). I.e., only components can specify providers.

As @Thierry mentions in his answer, each component in the component tree will get an associated "injector" if the component has a providers array specified. We can think of this like an injector tree, that is (normally much) sparser than the component tree. When a dependency needs to be resolved, this injector tree is consulted. The first injector that can satisfy the dependency does so. The injector tree is walked up, toward the root component/injector.

So, in order for your service to inject a configuration object dependency, that config object first has to be registered with an injector. I.e., in a component's providers array, call
provide(stringToken or OpaqueToken, {useValue: MyConfigObject} )
This registration must occur somewhere at or above the component where you want to use/inject your service.

Your service should then be able to @Inject the registered config object, because it will find it in the injector tree.

Note, since only components can configure providers, the @Injectable() decorator does not support any configuration options, so a providers array is not supported.