|Perl: the Markov chain saw|
Re: Design Patterns Still Aren'tby sharkey (Scribe)
|on Aug 21, 2003 at 05:10 UTC||Need Help??|
In defence of the Perl Design Patterns, I thought they were quite refreshing, and protrayed well how design patterns should be appropriately used in perl. There *is* a lot of hype around design patterns, and much of it *needs* to be deflated.
"Simple things should be simple" is the perl mindset, and the article does an excellent job of showing how to use them simply and effectively.
Design Patterns are a prime example of academic self-indulgence, where everything *must* be complex, because simple things are not publishable. Even the simplest pattern, Singleton, is an exercise in seeing how much complexity one can layer on top of a global variable, while providing zero benefits, and lingering problems. (Did anyone notice the note about timely and correct destruction being non-trivial--in the Knuth sense of the word?) In the end you have a Class in your global namespace instead of a variable, and a lot of useless, bloated code.
Patterns aren't Language Features. Maybe they aren't in java or C++, but if they *are* in perl or ruby, does that mean we still have to code it ourselves to make it a pattern? This is *exactly* the kind of artificial-complexity that turns design patterns into a tool of evil.
I'm not saying that patterns are always useless and bloated. (Well, maybe Singletons are.) They have their uses for solving complex problems, but not all problems are complex, and not all implementations need to be complex. Unfortunately, a culture of complexity has grown around design patterns, such that average programmers have a hard time applying or implementing them correctly. (I say that after having to fix applications by removing the design patterns from them.)
Patterns aren't Universally Applicable. and ... how a particular problem fits with a particular solution. Accepted patterns are too complex to be univerally applicable, but too many programmers try to apply them to everything anyway. You should be looking for solutions to your problems, not problems for your solution! It would help immensely if we could dispense with the complexity, and recognize iteration, repetition, and decision as valid patterns. Then patterns *would* be universally applicable, and it would be OK to apply simple solutions to one's problems.
Patterns aren't Platonic Ideals ... a ten-year-old collection of patterns from a different language. Um, well said. :) The problem with "distinctly named" patterns is that they become canonic: you should do it this way, even if perl has an easier and better way of doing it. Perl Design Patterns was trying to show the easier and better ways of doing it, instead of showing how to write 10-year-old C++ programs in perl. Is there something wrong with that?
Patterns aren't Total Solutions: ... The description of each pattern should review the context in which it is used, acknowledge the tradeoffs involved, and refer to other patterns that offer an alternative approach. First, I agree completely. Second, when was the last time you included comments like this in your code? (Oh wait, we only have to justify the pattern when we invent it, not when we use it, because any use of a pattern must be better than a non-pattern.) If people actually considered the tradeoffs involved (and documented them), complex patterns would only be used where the complexity is appropriate and necessary, or find a simpler way to do it.
Patterns aren't Generic Concepts. So looping is not a pattern because it is too generic? Why should I use a loop when an iterator will work just as well? It makes me feel elite, because I've written 10kLOC today.
Design Patterns provide solutions for problems, and standardize the names for those solutions. This is good.
Design Pattern Culture worships complexity to the point were any simple solution is rejected as a design pattern, and thus tacitly rejected as a solution. This is evil.