Interfaces are amazing things. When I was young and green, I didn’t understand their purpose, but after working with them for a while, I will defend their use to the end. I try to create lots of interfaces early on in my projects and I find that by keeping things flexible, it saves more time despite the extra typing, pardon the double entendre.
But this is not an article about why interfaces are so great. No, this is an article about the mysterious gap in the Flash Player API with regards to an interface for DisplayObjects. If you have a class typed as something like IView, there’s no way to enure that IView can be a parameter of display list functions like addChild().