Slides from my latest talk (and videos) about Angular dependency
injection, You can find related videos here: https://www.youtube.com/playlist?list=PLfZsWIHsTcftJl7WlidsXSBAHBXQBR4j2
36. Use an `InjectionToken` whenever the type you
are injecting is not rei
fi
ed (does not have a
runtime representation) such as when injecting an
Interface, callable type, array or parameterized type.
From the source