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Is there a metric analogous to the McCabe Complexity measure to measure how cohesive a routine is and also how loosely (or tightly) coupled the routine is to other code in the same code base?

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2 Answers 2

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I think the metric you are looking for is LCOM4, although it applies more to classes.

Sonar explains it nicely here:

...metric : LCOM4 (Lack Of Cohesion Methods) to measure how cohesive classes are. Interpreting this metric is pretty simple as value 1 means that a class has only one responsibility (good) and value X means that a class has probably X responsibilities (bad) and should be refactored/split.

There is not any magic here, only common sense. Let’s take a simple example with class Driver. This class has two fields : Car and Brain, and five methods : drive(), goTo(), stop(), getAngry() and drinkCoffee(). Here is the dependency graph between those components. There are three blocks of related components, so LCOM4 = 3, so the class seems to have three different responsibilities and breaks the Single Responsibility Principle. https://i.sstatic.net/2527G.png

...

It's a great tool, if you can use it. :)

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  • @OnorioCatenacci No problem. :)
    – Oleksi
    Commented May 31, 2012 at 15:40
  • Just too bad they don't go into how they calculate the metric. Commented May 31, 2012 at 15:44
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    This might help with that: aivosto.com/project/help/pm-oo-cohesion.html
    – Oleksi
    Commented May 31, 2012 at 15:46
  • Out of curiosity, how would you refactor that diagram to obey the Single Responsibility Principle? brain.setAngry(driver)? car.applyBreaks(driver)?
    – Phil
    Commented Nov 21, 2013 at 20:24
  • I doubt that code-based cohesion metrics can truly be indicative of interface level cohesion, and may even promote bad programming: mortoray.com/2015/04/29/… Commented May 4, 2015 at 8:23
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  • Afferent coupling: Number of responsibilities
  • Efferent coupling: Number of dependencies
  • Instability: Ratio of efferent coupling to total coupling (Afferent + Efferent).

Instability is supported in various code metric tools.

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  • Thanks @Brian--exactly the sort of thing I was hoping to find. Commented May 31, 2012 at 15:05

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