Refactor your code: when, why and how?
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Have you always heard about refactor and it always sounded like a foreign language to you? Have you tried to change code several times but found it impossible to make such changes in several projects? Do you feel overwhelmed when working with legacy code? Let's see the benefits of refactoring your code and see some tips on how to do it safely! We will start talking about what is legacy code, what we understand about refactoring and why it is so important nowadays when in most cases we work with software that others have written. Later we will share when we should start thinking on refactoring code. Finally, we will see in a live coding session some of the most important and useful refactoring techniques we could apply in our day-to-day job. At the end of this session, I hope you may have learned some tips on how to work with legacy code and how to apply certain techniques to make your day to day more enjoyable ;-) === * Presentation shared at Jconf Mexico on October 3rd, 2020: https://convoca.dev/jconf-mexico-2020/talk/FMDT8Z/
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Refactor your code: when, why and how?
- 1. Refactor your code: when, why and how?
- 2. 2Confidential Nacho Cougil • Senior Software Engineerat Dynatrace • TDD &cleancode fan • Founderof the Barcelona Java Users Group ( BarcelonaJUG ) & co-founderof the Java andJVMBarcelona Conference ( JBCNConf) • Father, formermountain marathonrunner 😅 @icougil WhoamI?
- 3. Confidential 3 • What is legacy code? • What is refactor? • Why refactor is {so }important? • When to refactor code? • Tips for refactoring • How to do it? • Recap Agenda
- 4. Confidential 4 Whatislegacycode? • “Legacy code is everythingthat is not tested“ MichaelFeathers • “Today, I stopped refactoring. Todaymyapplication became legacy” VictorRentea • “Valuable code weare afraid to change” J.B.Rainsberger
- 5. Confidential 5 • …do not understand what a particular code does and why? • ... wehave to workwith themaximum care because we understand that there can be manyproblems (surgeon mode) • ... weare afraid to touch the code Haveyoufelt thatsensation?
- 6. Confidential 6 Whatisrefactoring? • Refactoring is a disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behaviour • Refactoring is intended to improve the design, structure, and/or implementation of the software (its non-functional attributes), while preserving its functionality • So the main goal is… about: • Improving maintainability • Better readability • Reduce complexity • https://en.wikipedia.org/wiki/Code_refactoring • “A change made to the internal structure of software to make it easier to understand and cheaper to modify without changing its observable behaviour” Martin Fowler
- 8. 8Confidential • Broken windows theory (1982) • “A successful strategy for preventing vandalism, according to the book's authors, is to address the problems when they are small” • Minorcode smells mightlead to completely degenerated functions, classes, packages software became complicated &more difficult to maintain Whyis refactoring important? https://en.wikipedia.org/wiki/Broken_windows_theory
- 9. 9Confidential • Preparatory • BeforeI need to add a newfeatureor to fix a bug • As whendoing anexperiment -orcooking- probably you may needto arrangethescenarioproperly (ex: preparing theenvironment, collecting theproducts you need, etc) • As whentravelling,wemay needto checkthe map and find thebest routebefore moving Whento refactor?
- 10. 10Confidential • Comprehension • Whenweneedto understand the codebeforewe change it • Do I understand what this code does? Should I refactor it? • “We are moving our understanding from our head into the code itself“ WardCunningham • Whenthe codegetsclearer,wecanfind things on the design that wecould not seebefore Whento refactor?
- 11. 11Confidential • Litter-pickup • The code is doing something in a bad way (repeated code, high complexity, etc) • BoyScoutrule:“always leave the campground cleaner than you found it” • Small things ALWAYS matters! • Renaming avariable tomake it more understandable • Creating amethod that encapsulates a logic • Building a new class that holds a particularbehaviour • Remove unnecessary comments /dead code Whento refactor?
- 12. 12Confidential • Planned • Weneed a dedicated timeto get theircode base into a better state for the future • It maybe a sign that teams areworkingto pay off an unpaid technical debt • VSdoing it continuouslyas part of yournaturalflow of programming(ex: TDD,pair programming) Whento refactor?
- 13. 13Confidential • Long-term • The effort tomake the change is significantly higher (weeks vs hours/few days?) • Theeffort of changingthe status of the code is better than rewriting it (ex: fix some dependencies inour project, replace an existing library, etc) • A dedicated team to workon it VSgradually workon the problem Whento refactor?
- 14. 14Confidential • Continuously • Include refactoring as a normalactivity in yourday-to-day job • Less effort to do it insmall steps than inbig ones • More easily adapted when following XP practices (ex: TDD, codereviews, CI,etc) • “Just do it” fast feedback loop will makeyou programfaster Whento refactor?
- 15. Confidential 15 • Build a safety net that gives youtheconfidence to make changes • Workwith small steps &increments • Keep the code simple (as muchas possible) • Runyour tests ✅ after each change • Review 👀 your code coverage • Usethe tool 🛠 that could work {better }for you.Then, master it! Tips
- 16. Confidential 16 Tips- How to start? Start testing from the shortest branch Start refactoring fromthe deepest branch
- 17. Confidential 17 Catalogofrefactorings • 60refactorings • https://www.refactoring.com/catalog/
- 19. Confidential 19 Warning –Live coding!
- 20. Confidential 20 • Sandro Mancuso • https://youtu.be/_NnElPO5BU0 • Dave Farley • https://youtu.be/p-oWHEfXEVs • Jason Gorman • https://youtu.be/TSQVb2QoP2A • Victor Rentea • https://youtu.be/iOYsxBvMkLk • NayanHajratwala • https://youtu.be/1_X9ObRZkk4 Recommendedcontent
- 21. Confidential 21 • Importanceof refactoring • Different typesof refactoring • {Build &use }a safety net 🛠 • Usethe % coverage to guide 🛠 you • Understand (&apply) the seam 🛠 technique • Workwith small increments (useyour DVCS) • Design yoursoftware with testability inmind • Rememberthe boyscout rule! 😉 • Practice, practice &practice 🛠 again Finalrecap
- 22. 22Confidential [email protected] [email protected] https://nacho.cougil.com @icougil I’d love 😍 to receive yourfeedback, please: https://bit.ly/refactoring-feedback-nacho Questions?
Editor's Notes
- #5: (It‘s about information and safety)
- #7: make it easier to understand and cheaper to modify (without changing the observable behavior of the software)
- #8: Design stamina hypothesis: - at some point new features requires more time to see how to fit into the existing code base - by putting our effort into a good internal design, we increase the stamina of the software effort, allowing us to go faster for longer
- #9: Broken windows theory (1982): a criminological theory that states that visible signs of crime, anti-social behavior, and civil disorder create an urban environment that encourages further crime and disorder, including serious crimes.
- #20: https://github.com/sandromancuso/trip-service-kata.git - Seam: “A seam is a place where you can alter behavior in your program without editing in that place.” Excerpt From: Michael C. Feathers. “Working Effectively with Legacy Code”.
- #21: GOOST >> TDD learn, understand & apply Refactoring to patterns >> shows incremental changes made to transition from a problematic start to the pattern-based end point
- #23: Nacho