title: When does the constructor of an injected service in angular run?
body: <p>In Angular 7, if we have a service declared as @Injectable({providedIn: 'root'}), when does it's constructor execute? Does it execute upon the construction of a component that uses it (as a dependency) or does it wait until a method in that service is first called?</p>
  
  <p>Note:
  Since the service is a singleton, I use the service's constructor to initialize some values. I could create a "Initialize()" method and call that in the component's constructor instead but I find this aproach a little messy.</p>