Matthias Noback has posted a continuation of his previous article covering unary call sites and interfaces with this new tutorial with a way to reduce these call sites by making effective use of dependency injection and passing values with the correct context.

While reading David West's excellent book "Object Thinking", I stumbled across an interesting quote from David Parnas on the programming method that most of us use by default [about the process a machine uses to execute code]. It may seem like a very logical thing to do. And it's what I've seen myself and many other programmers do: "How do we implement this feature?"

[...] I described one situation in a previous article about read models, where I realized that we often try to answer many different questions by querying one and the same model (which is also the write model). By splitting write from read, we end up with a more flexible design.

The same goes for introducing interfaces, to achieve dependency inversion. We do a little extra work, but we thereby allow ourselves to get rid of a bit of "computer think".

He goes on to talk about singletons, service locators and registries and how dealing with them can get complex relatively quickly. He then shares a few possible solutions in the form of dependency injection and passing in the items needed for context rather than pulling them from another object. He ends the post with a summary of the combination of these two methods, showing how they can reduce the number of overall "call sites" for pieces of functionality in your application.