Conclusion

So, we made it. We started with a design problem and, through reasonable evolution, brought it pretty close to the canonical OBSERVER pattern. You might complain that since I knew that I wanted to arrive at the OBSERVER, I simply arranged it so that I would. I won't deny it. But that's not really the issue.

If you are familiar with design patterns, an appropriate pattern will very likely pop into your mind when you're faced with a design problem. The question, then, is whether to implement that pattern directly or instead to evolve it into place through a series of small steps. This chapter showed what the second option is like. Rather than simply leaping to the conclusion that the Observer pattern was the best choice for the problem at hand, I slowly maneuvered the code in that direction.

At any point during that evolution, I could have found that my problem was solved and stopped evolving. Or, I might have found that I could solve the problem by changing course and going in a different direction.

I drew in this chapter some of the diagrams for your benefit. I thought it would be easier for you to follow what I was doing by showing you an overview in a diagram. Had I not been trying to expose and expound, I would not have created them. However, a few of the diagrams were created for my benefit. There were times when I simply needed to stare at the structure that I had created so I could see where to go next.

Had I not been writing a book, I would have drawn these diagrams by hand on a scrap of paper or a whiteboard. I would not have taken the time to use a drawing tool. There are no circumstances that I know of in which using a drawing tool is faster than using a napkin.

Having used the diagrams to help me evolve the code, I would not have kept the diagrams. In every case, the ones I drew for myself were intermediate steps.

Is there value in keeping diagrams at this level of detail? Clearly, if you are trying to expose your reasoning, as I am doing in this book, they come in pretty handy. But usually, we are not trying to document the evolutionary path of a few hours of coding. Usually, these diagrams are transient and are better thrown away. At this level of detail, the code is generally good enough to act as its own documentation. At higher levels, this is not always true.