Refactoring: Invert Dependency With Observer | #53

Another refactoring today: Use the observer pattern to invert an infelicitous dependency. In and of itself, this is a modest refactoring, but its smell often co-presents with others, and unravelling it all can be tricky. (Note: We aren't remotely done talking about first and second-order refactorings, there are plenty more to go. But I'm not writing a catalog, I'm working a project, so when a hefty one like this comes along, that's when I'm talking about it. You're gettin' em as I'm doin' em.) "Infelicitous dependency", eh? What could make a dependency an unhappy one? There are a lot of possibilities, but for me they usually amount to one of two cases: 1) an important abstraction is dependent on an unimportant detail, 2) it keeps me from writing a test I want to write. A concrete example might help, and I have just the infelicitous dependency we need for this, because it fits both bills, being both a "wrong direction" dependency and an inherently anti-testing class. Aren't we just terribly terribly lucky? --- You can read the full transcription of this podcast over on GeePawHill.org. Any feedback, you can always tweet @GeePawHill on Twitter, or drop a voice message via the voice messages link here on Anchor. If you are interested in becoming more involved in the Change-Harvesting community, click here to learn about GeePaw's Camerata.