include FooCafe

author = Presenter.new(:buren)
slides = MigratingLegacy::Slides.new

wait until author.ready?

author.present(slides) do |slide|
  print slide
  any_questions? if slide.last?
end

Goto: http://jacobburenstam.com/migrating-legacy

GOTO

jacobburenstam.com/migrating-legacy

Who wants pizza?

Who here have worked with a legacy code base?

Where did/do you have the most "legacy"?

How do you battle legacy?

Agenda

Talk.......
- Please interupt me!
Code

Disclaimer

My on personal opinions, not the opinions of my employer.
Your mileage may vary (a lot)

Jacob Burenstam

Open source tinkerer
Useless code enthusiast
Work @ Trialbee

Legacy code

Definition?

Legacy code has many definitions:

Code for {outdated|obsolete} systems that is kept for {compatibility|legal|SLA} reasons
Code written by another person who don't maintain it anymore
Code without test (Micheal Feathers)

Legacy code in images

Keep it simple stupid!

Legacy code..

"... A large part of the task of a software engineer is to continually alter code to prevent this."

Wikipedia

Many ways to battle legacy code

There is no silver bullet
Be pragmatic, very pragmatic

Michael Feathers on improving legacy code

Identify change points
Find an inflection point (a small interface)
Cover the inflection point
- Break external dependencies
- Break internal dependencies
- Write tests
Make changes
Refactor the covered code.

Inspiration

"The functional core and the imperative shell"

Gary Bernhardt

https://www.destroyallsoftware.com/talks/boundaries

Remember the code from the first slide?

include FooCafe

author = Presenter.new(:buren)
slides = MigratingLegacy::Slides.new

wait until author.ready?

author.present(slides) do |slide|
  print slide
  any_questions? if slide.last?
end

DEADLINE = Time.new(2015, 10, 14, 18, 0, 0).freeze
module FooCafe;end
module FooCafe::MigratingLegacy;end
String.class_eval { define_method(:last?) { false } }
NilClass.class_eval { define_method(:last?) { true } }
define_method(:wait) { puts 'Still not ready..';sleep 3 }
define_method(:any_questions?) { puts 'Any questions?' }
define_method(:feedback) { puts 'Feedback?' }
class FooCafe::Presenter < Struct.new(:name)
  define_method(:ready?) { Time.now >= DEADLINE }
  def present(slides); slides.to_a.each { |slide| yield(slide) };end
end
class FooCafe::MigratingLegacy::Slides
  define_method(:initialize) { @slides = File.read('slides.md').split('---') }
  define_method(:to_a) { @slides + [nil] }
end

This actually makes the previous code work

http://git.io/vnWsf

GitHub logo

Slides available on

https://github.com/buren/migrating-legacy