Use Dependency Injection with ES6 and Angular

In this lesson, we are going to talk about dependency injection in an Angular application in ES6. There is a gotcha that I want to point out that most people will run into especially if they have not spent a lot of time using a classical language. We will start with a contrived example and then anchor it back into our application when we modify our CategoriesModel to use the $q service to return a promise.