CSC/ECE 517 Fall 2013/ch1 1w07 d

Background

The practice of code refactoring deals with changing the content or structure of code without changing the code's function in its execution. Code refactoring has become a standard programming practice, as it potentially promotes readability, extensibility, and reusability of code.

Whether done through an IDE or by hand, large-scale code projects can prove tedious to refactor. If minimal non-functional benefits are achieved through refactoring, time is wasted. Furthermore, if not done properly, code refactoring can actually break the functionality of the code.

Metrics

There are a variety of metrics that are used to quantify the merits of refactoring.

Complexity

In general, complexity is a measure of the number of branches and paths in the code.

Cyclomatic complexity, in particular, is a popular metric for measuring a method's complexity. In its simplest form, cyclomatic complexity can be thought of as adding 1 to the number of decision points within the code. <ref> http://www.codeproject.com/Articles/13212/Code-Metrics-Code-Smells-and-Refactoring-in-Practi</ref> These include cases in switch statements, loops, and if-else statements.

public void makeDecision(condition) {
  if(condition a) {
    choose(a);
  }
  else {
    choose(b);
  }
}

In this example, there are two decision points, so the cyclomatic complexity is 2+1=3.

Cyclomatic complexity values are divided into tiers of risk, where values less than 20 are of low-to-moderate risk, values between 20 and 50 are of high risk, and values greater than 50 are of extreme risk. <ref>http://www.klocwork.com/products/documentation/current/McCabe_Cyclomatic_Complexity</ref>

References

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