This post originated from an RSS feed registered with Agile Buzz by Keith Ray. Original Post: Minimal To Humane Feed Title: MemoRanda Feed URL: http://homepage.mac.com/1/homepage404ErrorPage.html Feed Description: Keith Ray's notes to be remembered on agile software development, project management, oo programming, and other topics. Latest Agile Buzz Posts Latest Agile Buzz Posts by Keith Ray Latest Posts From MemoRanda

A bit more on the Humane Interfaces and Minimal Interfaces debate that I blogged about previously. Some people think XP's "YAGNI"(You Aren't Going to Need It) rule that prevents unnecessary work means XPers are in favor of Minimal Interfaces, but that is only to start with. Refactoring away code duplication (and other code smells that the Simplicity Rules are against) tends to create Humane Interfaces.

For example, if I was doing test-driven development in an environment that didn't already have a list class, and one was needed, I would test-drive a minimal implementation: maybe all it has to start with is list.size(), list.at(int index), list.add(object), and list.removeAt(int index). However, as the list gets used, I would look for duplicate code. If I refer to the first element using list.at(0) in more than one place, adding list.first() to the list class would remove duplication (the OnceAndOnlyOnce part of the Simplicity Rules). If I have code like this...

x = nil;
if ( list.size %gt 0 )
    x = list.at( list.size() - 1 );

... I don't even need duplication to want to refactor that piece of code into a method of the list class. You'll note those three lines of code have the code smell "Many messages to the same object from the same method" (3 is "many" here), or "asking instead of telling" (we need some pithy standardized names for code smells). Refactoring that code into "list.last()" follows the Simplicity Rule "Expresses every idea that we need to express" (aka "Self Documenting Code", aka "Intention-Revealing Code"). Similarly if I search the list, enumerate the list, and so on, the rules of Simple Design would require that I move those features into the list class as well to clearly express intention and avoid duplication.

So as the project progresses, the list class moves from being a very minimal interface to being a humane one, without ever having a method that isn't used in the project.

Library(framework) design often starts in a vacuum, but wise people recommend using the library in three non-trivial applications before publishing it, precisely so that these kinds of refactorings can "tune" the library into something people will want to use, before publishing it.