Feeds

When code goes bad: What to watch for

Emergent Design: Pathologies uncovered

Providing a secure and efficient Helpdesk

Book extract, part five Scott Bain’s book, Emergent Design: The Evolutionary Nature of Professional Software Development by Addison Wesley, looks at the principles involved in building and maintaining robust, reliable, and cost-effective code. In this, our concluding extract, Scott identifies the pathologies in code when coupling, cohesion, and redundancy have not been adhered to.

It is important to know the qualities you want your code to have, but it is also important to empower yourself with a set of indicators that tell you that you are heading in the wrong direction. Ideally, I would like to know I am doing something I should not do before I have done very much of it. Also, we often are called upon to evaluate other people's code, or to revisit our own code from the recent or distant past.

Pathologies help us here. In truth, code, design, and system pathologies could be the subject of an entire book, but there are a few really high-leverage indicators that we can use as a basic set. Not surprisingly, they tie into the qualities that I listed earlier: coupling, cohesion, and eliminating redundancy.

Indicators of weak cohesion

Here are some indicators of weak cohesion:

  • Difficulty naming. I would like the names of classes, methods, and other entities (delegates, packages, and so on) to reveal their intentions in their names. I would also like my names to be relatively brief, and yet still tell the whole story.
  • When a class or method has a long name, or a vague name, the reason often is that a really informative name is very difficult to create, due to the fact that the class or method does a number of different things. This, of course, is weak cohesion, and causes lots of other problems anyway. When I cannot name things the way I want to, I suspect that my entities do too much.
  • Large tests. When a class has multiple responsibilities, it can create large tests, because the test must cover all the possible combinations of these responsibilities.
  • Large classes and methods. When a class or a method gets big and requires lots of scrolling in your integrated development environment, or when it is hard to see well, I usually suspect weak cohesion. This is not an absolute; algorithms themselves can get large and yet still be about one responsibility, but it is, at least, something to investigate when I see it.

A student once told me a story that is pretty illustrative and also kind of funny. He was given a class to refactor. Someone had written the class in C#, but clearly did not know much about object orientation. The class worked fine (the author had been, obviously, a skilled programmer), but nobody could or would touch it. It was, essentially, one huge method.

He started by doing what I would probably do; he just scanned through the code without really reading it thoroughly, just to determine how tough this job was going to be. He was, of course, being asked how long this was going to take.

As he scanned along, hitting Page Down over and over, suddenly all the code disappeared from the screen. A few more page downs revealed blank screen after blank screen, and then suddenly the code was back again.

Beginner's guide to SSL certificates

More from The Register

next story
ONE MILLION people already running Windows 10
A third of them are doing it in VMs, but early feedback focuses on frippery
Sign off my IT project or I’ll PHONE your MUM
Honestly, it’s a piece of piss
Netscape Navigator - the browser that started it all - turns 20
It was 20 years ago today, Marc Andreeesen taught the band to play
Torvalds CONFESSES: 'I'm pretty good at alienating devs'
Admits to 'a metric ****load' of mistakes during work with Linux collaborators
Sway: Microsoft's new Office app doesn't have an Undo function
Content aggregation, meet the workplace ... oh
Do Moan! MONSTER 6-day EMAIL OUTAGE hits Domain Monster
Customers freaked out by frightful service
Ploppr: The #VultureTRENDING App of the Now
This organic crowd sourced viro- social fertiliser just got REAL
Return of the Jedi – Apache reclaims web server crown
.london, .hamburg and .公司 - that's .com in Chinese - storm the web server charts
NetWare sales revive in China thanks to that man Snowden
If it ain't Microsoft, it's in fashion behind the Great Firewall
prev story

Whitepapers

Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
Win a year’s supply of chocolate
There is no techie angle to this competition so we're not going to pretend there is, but everyone loves chocolate so who cares.
Why cloud backup?
Combining the latest advancements in disk-based backup with secure, integrated, cloud technologies offer organizations fast and assured recovery of their critical enterprise data.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
Saudi Petroleum chooses Tegile storage solution
A storage solution that addresses company growth and performance for business-critical applications of caseware archive and search along with other key operational systems.