Using Code Metrics for Targeted Code Refactoring

The knowledge of how to effectively spot smelly code and replace it with proven patterns will ultimately lead to a more stable, maintainable and elegant code base.

Often times, candidate code for refactoring is based upon a source file's smell, which its spotting can take time to acquire and is largely based upon subjective determinations. The proper use of code metrics, such as Cyclomatic Complexity, Fan-In, Fan-Out, and Depth of Inheritance can also facilitate the discovery of candidate code which is in need of refactoring.

For example, Cyclomatic Complexity is adept at spotting methods containing a high degree of conditional logic, which, consequently, can be replaced with polymorphism as elaborated in Martin Fowler's seminal work, Refactoring with the Replace Conditional with Polymorphism pattern. Additionally, excessively deep hierarchy trees create problematic testing targets, which can be broken out into separate objects with Fowler's Replace Inheritance with Delegation and Collapse Hierarchy patterns. Fan-In and Fan-Out are quite effective at pinpointing brittle code, which can be refactored into a more stable state with a plethora of patterns including Extract Hierarchy and Extract Class.

About Andrew Glover

Andrew is the Engineering Manager for Netflix's Delivery Engineering Team. He and his team are building the next generation Continuous Delivery platform that is facilitating Netflix's rapid global expansion. Before joining Netflix, he served as the CTO of App47, where he lead the development of a SaaS Mobile Application Management platform. Andrew is also the co-author of Addison Wesley's “Continuous Integration” and he actively blogs about software at thediscoblog.com.

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