Goals of refactoring? [closed]

Question

What are the goals of refactoring code? Is it only to enhance the code structure? Is it to pave the way for future changes?

Answer 1

Understandability

More straightforward and well organized (factored) code is easier to understand.

Correctness

It's easier to identify defects by inspection in code that's easier to understand. Overly complex, poorly structured, Rube Goldberg style code is much more difficult to inspect for defects. Additionally, well componentized code with high coherency of components and loose coupling between components is vastly easier to put under test. Moreover, smaller, well-formed bits under test makes for less overlap in code coverage between test cases which makes for faster and more trustworthy tests (which becomes a self-reinforcing cycle driving toward better and better tests). As well, more straightforward code tends to be more predictable and reliable.

Ease of Maintenance and Evolution

Well-factored, high quality, easy to understand common components are easier to use, extend, and maintain. Many changes to the system are now easier to make because they have smaller impact and it's more obvious how to make the appropriate changes.

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Refactoring code does have merit on its own just in terms of code quality and correctness issues, but where refactoring pays off the most is in maintenance and evolution of the design of the software. Often a good tactic when adding new features to old, poorly factored code is to refactor the target code then add the new feature. This often will take less development effort than trying to add the new feature without refactoring and it's a handy way to improve the quality of the code base without undertaking a lot of "pie in the sky" hypothetical advantage refactoring / redesign work that's hard to justify to management.