What is the deal with software patterns?

2018-10-12

If you’re someone who has always programmed in a very high level language such as Python, you may have wondered: “What is the deal with the Gang of Four software patterns book anyway?!”

The GOF idea of a pattern is inspired by a wonderful planning and architecture book called A Pattern Language. It’s a gem! It’s in your local library!

Here’s a representative example (and some good advice):

Whenever you build a balcony, a porch, a gallery, or a terrace always make it at least six feet deep. If possible, recess at least a part of it into the building so that it is not cantilevered out and separated from the building by a simple line, and enclose it partially.

This instruction is preceded by a couple of hundred words of justification, including:

Balconies and porches which are less than six feet deep are hardly ever used.

There are 253 of these patterns. They’re practical, concrete advice. They’re generic, but they’re not abstract.

The GOF patterns are very different in character. They manage to pull off the trick of being both very abstract and very low level. As a result, the book has had relatively little practical impact on day-to-day software engineering, despite its high profile.

Don’t take my word for this. This fantastic Brian Marick talk does a great job of explaining why Pattern Language works and the GOF book didn’t.

In hindsight then, the GOF book didn’t really work. But while its low level and abstract patterns are not useful to most of us (because they’re low level and abstract!), they great things for language designers to bear in mind.

Python’s designers and those of many other modern languages did exactly that, and made these patterns part of the syntax, as explained so well in Brandon Rhode’s guide to the GOF patterns and their applicability to Python. (Brandon’s site is also a great place to start if you are unclear on what a design pattern even is.)

So, the moral of the story is: the GOF patterns are not something most of us need to worry about when we create applications because

1. they are not actually that useful for application development in any language, and
2. if you’re using a modern language, they are probably built in to syntax of (or made redundant by the design of) the dang language anyway

But despite that you should watch Brian’s talk and check out Brandon’s patterns site.