Feeds

When code goes bad: What to watch for

Emergent Design: Pathologies uncovered

Website security in corporate America

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.

Choosing a cloud hosting partner with confidence

More from The Register

next story
'Windows 9' LEAK: Microsoft's playing catchup with Linux
Multiple desktops and live tiles in restored Start button star in new vids
Not appy with your Chromebook? Well now it can run Android apps
Google offers beta of tricky OS-inside-OS tech
New 'Cosmos' browser surfs the net by TXT alone
No data plan? No WiFi? No worries ... except sluggish download speed
SUSE Linux owner Attachmate gobbled by Micro Focus for $2.3bn
Merger will lead to mainframe and COBOL powerhouse
iOS 8 release: WebGL now runs everywhere. Hurrah for 3D graphics!
HTML 5's pretty neat ... when your browser supports it
Greater dev access to iOS 8 will put us AT RISK from HACKERS
Knocking holes in Apple's walled garden could backfire, says securo-chap
NHS grows a NoSQL backbone and rips out its Oracle Spine
Open source? In the government? Ha ha! What, wait ...?
Google extends app refund window to two hours
You now have 120 minutes to finish that game instead of 15
Intel: Hey, enterprises, drop everything and DO HADOOP
Big Data analytics projected to run on more servers than any other app
prev story

Whitepapers

Providing a secure and efficient Helpdesk
A single remote control platform for user support is be key to providing an efficient helpdesk. Retain full control over the way in which screen and keystroke data is transmitted.
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.
Security and trust: The backbone of doing business over the internet
Explores the current state of website security and the contributions Symantec is making to help organizations protect critical data and build trust with customers.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
Security for virtualized datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.