Ruby Meditation #2 April 6, 2013 Kyiv

1. How to f*ck up
the refactoring
The ultimate guide
Saturday, April 6, 13

2. Situation
Saturday, April 6, 13

3. •2 developers
Saturday, April 6, 13

4. •2 developers
•2 projects
Saturday, April 6, 13

5. •2 developers
•2 projects
•Near the same stage
Saturday, April 6, 13

6. Project1
• Written by novice
Saturday, April 6, 13

7. Project1
• Written by novice
• Full of code duplication
Saturday, April 6, 13

8. Project1
• Written by novice
• Full of code duplication
• Denormalized data structure
Saturday, April 6, 13

9. Project1
Still maintainable
Saturday, April 6, 13

10. Project2
• Written by more experienced developer
Saturday, April 6, 13

11. Project2
• Written by more experienced developer
• No code duplication
Saturday, April 6, 13

12. Project2
• Written by more experienced developer
• No code duplication
• No data duplication
Saturday, April 6, 13

13. Project2
Maintainable through rewrite
Saturday, April 6, 13

14. Saturday, April 6, 13

15. @ptico
}Github
Twitter
LinkedIn
Andrey Savchenko
Aejis
Saturday, April 6, 13

16. Refactoring
anti-patterns
Saturday, April 6, 13

17. “IDD”
Intuition Driven Development
Saturday, April 6, 13

18. lib/extensions.rb________
class Hash
def to_ostruct
# Convert text to ostruct
end
end
module Wicked::Controller::Concerns::RenderRedirect
def process_resource!(resource)
# processing staff
end
end
Saturday, April 6, 13

19. app/controllers/application_controller.rb
module AjaxActions
def users_list
render :json => @users
end
end
Saturday, April 6, 13

20. lib/model_helper.rb
module ModelHelpers
def as_json(*)
super(:include => :logs)
end
end
Saturday, April 6, 13

21. Howtoprevent
• Do not do refactor unless you know
exactly what you do
• Do not assign refactor tasks to the juniors
• Learn design patterns
Saturday, April 6, 13

22. “DRY Madness”
Saturday, April 6, 13

23. DRY does not mean “don’t type the
same characters twice”‟David Chelimsky
Saturday, April 6, 13

24. Bad
%(foo bar baz).each do |name|
define_method(:"set_#{name}") do |val|
val = val.to_s if name == "bar"
name = :"#{name}_name"
self.prev[name] = self.attributes[name]
self.attributes[name] = val
end
end
Saturday, April 6, 13

25. Good
def set_attribute(name, val)
prev[name] = attributes[name]
attributes[name] = val
end
def set_foo(val)
set_attribute(:foo_name, val)
end
def set_bar(val)
set_attribute(:bar_name, val.to_s)
end
def set_baz(val)
set_attribute(:baz_name, val)
end
Saturday, April 6, 13

26. tasks.do_the_task(:special, "foo")
tasks.do_the_task(:ordinal, "bar")
def do_the_task(type, val)
if type == :special
val = convert_val_for_special(val)
end
if type == :ordinal && val.is_a?(String)
self.is_string = true
end
self.type = type
self.state = :done
self.val = val
save
end
Bad
Saturday, April 6, 13

27. Good
def do_special_task(val)
val = convert_val_for_special(val)
persist_task(:special, val)
end
def do_ordinal_task(val)
self.is_string = true if val.is_a?(String)
persist_task(:ordinal, val)
end
def do_another_task
persist_task(:another, val)
end
def persist_task(type, val)
self.type = type
self.state = :done
self.val = val
save
end
Saturday, April 6, 13

28. Howtoprevent
• Don’t afraid to type twice - afraid to
implement twice
• Avoid metaprogramming
• Avoid metaprogramming
Saturday, April 6, 13

29. “Frankenstein”
Saturday, April 6, 13

30. class PigLivery
def filter(blood)
# do important things
end
end
class Pig
def initialize
@livery = PigLivery.new
# ...
end
end
Saturday, April 6, 13

31. - class PigLivery
+ class PigHumanLivery
class Human
def initialize
@livery = PigHumanLivery.new
# ...
end
end
def initialize
if for_human?
resize_a_bit
end
end
Saturday, April 6, 13

32. class FrankensteinMonster
def initialize
@livery = PigHumanLivery.new
@eyes = CatDogEyes.new
@jaw = MonkeyJaw.new
# ...
end
end
Saturday, April 6, 13

33. Howtoprevent
• Use OOP superpower (subclassing instead
conditions, etc.)
• Follow the interface segregation principle
Saturday, April 6, 13

34. “General content”
Saturday, April 6, 13

35. class GeneralContent
# Attrs: title, body, coords, tags
end
class Page < GeneralContent
# Uses: title, body, tags
end
class City < GeneralContent
# Uses: title, body, coords
end
class Hotel < GeneralContent
# Uses: title, coords, stars, tags
end
Saturday, April 6, 13

36. Howtoprevent
• Do not rebuild data structure while
business requirements is not finalized
• If you consciously do something like this —
try to change your profession
Saturday, April 6, 13

37. Common tips
Saturday, April 6, 13

38. Don’trefactor onearly
stages
Saturday, April 6, 13

39. You have enought time

Saturday, April 6, 13

40. Learndesign patterns
andprinciples
Saturday, April 6, 13

41. SOLID
GRASP
YAGNI
Saturday, April 6, 13

42. Usecommonsense
Saturday, April 6, 13

43. Saturday, April 6, 13

44. Questions?
Attributions:
Linecons by Sergey Shmidt
http://www.flickr.com/photos/amyn-design/8548659957/
http://www.flickr.com/photos/greenflames09/100781977/
Andrey Savchenko
Aejis
@ptico
Saturday, April 6, 13