TypeScript 2.x By Example

Managing the dependencies

In Angular, the framework determines what dependencies a specific class has and then injects those dependencies into the class at the time of object creation. So, taking from the above example, when Angular is creating an object of the Trello service class, it checks the constructor signature and identifies the dependencies that the Trello service needs.

In our case, it's only one, the HTTP module. Here Angular checks where the HTTP module resides, which it finds out from the definition in the app.module file. It then either creates a new instance or uses the existing instance and passes that to the Trello service constructor. 

This allows us to not have the responsibility of identifying the dependency and creating ...