Harry Potter and The Legacy Codebase

It's your first day at Hogwarts.com, and everything is wonderful and thrilling. You dig in to classes, and soon find a dusty book with a cryptic warning:

"Do NOT on any circumstances make ANY change to this magic incantation without talking to Doug first!!!"

Sound familiar? Approaching a legacy code base can feel like unraveling a mystery, not just about the code, but about the personalities who wrote it. What tools and techniques can help you solve the maze of twisty code? Let's explore how to get a handle on legacy code, how to negotiate joining an existing team of developers, and how we can get a summa cum laude at graduation.

Transcript

1. Harry Potter and The Legacy Codebase 1 Friday, February 21, 14
2. Harry Potter and The Legacy Codebase 2 Friday, February 21, 14
3. 3 Friday, February 21, 14
4. MINSWAN 4 Friday, February 21, 14
5. NIRD.us 5 Friday, February 21, 14
6. AdaDevelopersAcademy.org 6 Friday, February 21, 14
7. 7 Friday, February 21, 14
8. 8 Friday, February 21, 14
9. WHY YOU’RE HERE • House New Hire -- You’re a new developer joining an established team • House Reorg -- Hogwarts-Online reorg assigned this to you • House Feddup -- You’ve decided you’ve had enough and volunteered 9 Friday, February 21, 14
10. 10 Friday, February 21, 14
11. LEGACY CODE ISN’T EVIL, IT’S JUST MISUNDERSTOOD 11 Friday, February 21, 14
12. IDEAL HABITAT • Software that has been superseded but is difficult to replace because everyone and everything relies on it • Code without tests • Code that you didn’t write • Code written before today 12 Friday, February 21, 14
13. 13 Friday, February 21, 14
14. 14 Friday, February 21, 14
15. CODE ARCHEOLOGY 101 15 Friday, February 21, 14
16. 16 Friday, February 21, 14
17. CODE ARCHEOLOGY 101 • Achieve a better understanding of the overall architecture • Discover the root cause of a critical bug • Determine the best way to extend the functionality of a vestigial class • Investigate a previous approach to solving a current problem In this class you will learn how to... 17 Friday, February 21, 14
18. CODE ARCHEOLOGY 101 •Surveyance •Excavation •Analysis Each House will complete one of three tasks... 18 Friday, February 21, 14
19. BE BRAVE 19 Friday, February 21, 14
20. TO FALLEN COMRADES 20 Friday, February 21, 14
21. 21 Friday, February 21, 14
22. 22 Friday, February 21, 14
23. SURVEYANCE 23 Friday, February 21, 14
24. TAKE INVENTORY 24 Friday, February 21, 14
25. ASK DUMB QUESTIONS 25 Friday, February 21, 14
26. FLAG MYTHS 26 Friday, February 21, 14
27. Tricks ↓ Techniques ↓ Process ↓ Methodology ↓ Dogma 27 Friday, February 21, 14
28. class Basilisk < ActiveRecord::Base def remove_poison update!(ink_quantity: 0) end end 28 Friday, February 21, 14
29. class PoisonBarrel < ActiveRecord::Base def self.first_free_barrel(liters_needed) free = DEFAULT_CAPACITY - liters_needed InkBarrel.where("liters < ?", free) end def self.with_free_space(liters_needed) if self.first_free_barrel(liters_needed) return barrels.first else return PoisonBarrel.create! end end end 29 Friday, February 21, 14
30. class Basilisk < ActiveRecord::Base def remove_poison barrel = PoisonBarrel. with_free_space(poison_quantity) barrel.liters += poison_quantity barrel.save! update!(ink_quantity: 0) end end 30 Friday, February 21, 14
31. EXCAVATION 31 Friday, February 21, 14
32. 32 Friday, February 21, 14
33. "FIRST, DO NO HARM" 33 Friday, February 21, 14
34. class Basilisk < ActiveRecord::Base def remove_poison warn "#remove_poison has been deprecated. “ + “Use #harvest_poison instead." harvest_poison end def harvest_poison store_poison_in(poison_container, poison_quantity) update!(poison_quantity: 0) end private def store_poison_in(container, poison_quantity) container.first_with_free_space(poison_quantity). update!(liters: poison_quantity) end end 34 Friday, February 21, 14
35. ANALYSIS / DOCUMENTATION 35 Friday, February 21, 14
36. DOCUMENT EVERYTHING 36 Friday, February 21, 14
37. MAKE A MAP 37 Friday, February 21, 14
38. FINAL EXAMS 38 Friday, February 21, 14
39. 39 Friday, February 21, 14
40. ★ glass artist ★ Vespa mechanic ★ lighting designer ★ author & teacher ★ player of games ★ software developer @kerrizor KERRI MILLER 40 Friday, February 21, 14
41. 41 Friday, February 21, 14