TITLE: Points of Emphasis for Teaching Design AUTHOR: Eugene Wallingford DATE: June 12, 2014 2:29 PM DESC: ----- BODY: As I mentioned recently, design skills were a limiting factor for some of the students in my May term course on agile software development. I saw similar issues for many in my spring Algorithms course as well. Implementing an algorithm from lecture or reading was straightforward enough, but organizing the code of the larger system in which the algorithm resided often created challenges for students. I've been thinking about ways to improve how I teach design in the future, both in courses where design is a focus and in courses where it lives in the background of other material. Anything I come up with can be also part of conversation with colleagues as we talk about design in their courses. I read Kent Beck's initial Responsive Design article when it first came out a few years ago and blogged about it then, because it had so many useful ideas for me and my students. I decided to re-read the article again last week, looking for a booster shot of inspiration. First off, it was nice to remember how many of the techniques and ideas that Kent mentions already play a big role in my courses. Ones that stood out on this reading included:
Exploit Symmetries. Divide similar elements into identical parts and different parts.As I noted in my first blog about this article, many programmers find it counterintuitive to use duplication as a tool in design. My students struggle with this, too. Soon after that blog entry, I described an example of increasing duplication in order to eliminate duplication in a course. A few years later, in a fit of deja vu, I wrote about another example, in which code duplication is a hint to think differently about a problem. I am going to look for more opportunities to help students see ways in which they can make design better by isolating code into the identical and the different.
Inside or Outside. Change the interface or the implementation but not both at the same time.This is one of the fundamental tenets of design, something students should learn as early as possible. I was surprised to see how normal it was for students in my agile development course not to follow this pattern, even when it quickly got them into trouble. When you try to refactor interface and implementation at the same time, things usually don't go well. That's not a safe step to take... My students and I discussed writing unit tests before writing code a lot during the course. Only afterward did it occur to me that Inside or Outside is the basic element of test-first programming and TDD. First, we write the test; this is where we design the interface of our system. Then, we write code to pass the test; this is where we implement the system. Again, in upcoming courses, I am going to look for opportunities to help students think more effectively about the distinction between the inside and the outside of their code. Thus, I have a couple of ideas for the future. Hurray! Even so, I'm not sure how I feel about my blog entry of four years ago. I had the good sense to read Kent's article back then, draw some good ideas from it, and write a blog entry about them. That's good. But here I am four years later, and I still feel like I need to make the same sort of improvements to how I teach. In the end, I am glad I wrote that blog entry four years ago. Reading it now reminds me of thoughts I forgot long ago, and reminds me to aim higher. My opening reference to getting a booster shot seems like a useful analogy for talking about this situation in my teaching. -----