MVVM in iOS: who is the responsible for the assembly?

I'm trying to apply MVVM architecture in my iOS project and I've read some articles like this one where it is said that:

(...) we can make the app-wide Router service which will be responsible for performing assembly and the View-to-View presentation

But I don't find any code sample for this kind of class, I'd really appreciate that somebody could explain the appropriate way to implement such "Router" class for a MVVM assembly, or say where I could find an example.