What is the highest Cyclomatic Complexity of any function you maintain? And how would you go about refactoring it?

refactoring cyclomatic-complexity
JohannesH picture JohannesH · Sep 2, 2009 · Viewed 10.9k times · Source

I was doing a little exploring of a legacy system I maintain, with NDepend (great tool check it out), the other day. My findings almost made me spray a mouthful of coffee all over my screen. The top 3 functions in this system ranked by descending cyclomatic complexity are:

  1. SomeAspNetGridControl.CreateChildControls (CC of 171!!!)
  2. SomeFormControl.AddForm (CC of 94)
  3. SomeSearchControl.SplitCriteria (CC of 85)

I mean 171, wow!!! Shouldn't it be below 20 or something? So this made me wonder. What is the most complex function you maintain or have refactored? And how would you go about refactoring such a method?

Note: The CC I measured is over the code, not the IL.

Answer

Andrew Cowenhoven picture Andrew Cowenhoven · Sep 2, 2009

This is kid stuff compared to some 1970s vintage COBOL I worked on some years ago. We used the original McCabe tool to graphically display the CC for some of the code. The print out was pure black because the lines showing the functional paths were so densely packed and spaghetti-like. I don't have a figure but it had to be way higher than 171.

What to do

Per Code Complete (first edition):

If the score is:

  • 0-5 - the routine is probably fine
  • 6-10 - start to think about ways to simplify the routine
  • 10+ - break part of the routine into a second routine and call it from the first routine

Might be a good idea to write unit tests as you break up the original routine.

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