How to fix Angular 2 `Uncaught (in promise): TypeError: Cannot read property 'query' of null`?

Question

I\'ve been using the Heroes tutorial in the Angular 2 docs to experiment. However, I\'ve come to a point that I don\'t understand what\'s happening with this error:

Answer 1

I see the following problem: HeroComponent depends on HeroDetailsComponent, but HeroDetailsComponent is exported afterwards in the app/heroes/index.ts file.

Someone reported a problem with this kind of set up here