This document contains code snippets and discussions around conditional logic and control flow. It explores different approaches like if/else statements, case/when statements, polymorphism, and error handling. It also discusses design patterns like look before you leap versus easier to ask forgiveness than permission and how to structure conditional logic for readability, extensibility and reducing duplication.

1. Font Test: Liberation Sans
I am monospace font
and kinda important, 32pt,
Ok?
LibreOffice
ife!!!
“orange”?

3. J
July 2017
September 2019

8. TRB in 90 sec.TRB in 90 sec.TRB in 90 sec.
1.0
class CommentsController
def update
run Comment::Update
end
2.0
class Comment::Update < …::Operation
step :find_model
step :validate
step :save
fail :alert_admin
step :notify_admin
nd
2.1

9. Nightmare on
else Street
def run_circuit(options)
steps.each do |step|
trace(options, step) if TRACING == true
step.call(options)
end
end

10. The Story of Trailblazer 3.0
is The Story of ifs.
2.1

11. if
Nick Sutterer

12. If is like vodka.
If you over-use it,
you get a headache.

13. Operative ifs vs. structural ifs
if email =~ /@/
else
end
if user.status == :suspended
&& action == :vote
raise “not allowed”
else
end

14. Business processes will always be
complex, son. There ain’t no way
to, like, simplify those.
But there are good and, eh, bad
tools to deal with… yeah, right,
complexity!
– Donald Trump, 1644
“

15. Pull
Requests,
yay!

16. + if MYCOMPANY == true
+ img_path = “mycomp/imgs” + “hi.jpg”
+ img = image_tag(path)
+ section = content_for(:blog, img)
+ else
img_path = “/imgs” + “hi.jpg”
img = image_tag(path)
section = content_for(blog_name, img)

17. Milestone Codename
1.2.3 “Hello world”
2.0.0 “Hello world” 2.0.0
3.0.0 The Merb merge™
3.1.0 @wycats’s Revenge
4.0
5.0 Chatbot
6.0 Typo3 Drupal
X
rails$ wc -l respond_to?
129
if association.respond_to?(:to_ary)

18. Duck typing?
An object's suitability is determined by
the presence of certain methods [..],
rather than the type of the object itself.
– Wikipedia

19. LBYL
Look before you leap.
if
EAFP
Easier to ask for forgiveness than permission.
try/rescue

20. Compressive behavior of CNT in
polymer matrix with strong interfaces

21. obj.method_i_know #=> yay, works
obj.unknown_method #=> throw a
fucking
exception

22. class Developer
implements Attendee
def drink_shot()
end
end
class HRManager
implements Attendee
def drink_shot()
end
end
def celebrate(attendee)
attendee.drink_shot()
end
def celebrate(Attendee attendee)
attendee.drink_shot()
end

23. STATIC
TYPING def celebrate(Attendee attendee)
celebrate(conference)
#=> compile-time error <3
if obj.is_a?(Conference)
raise “wrong argument!”
elsif obj.is_a?(Attendee)
# do it!

24. Method
Overloading
def celebrate(Attendee user)
user.drink_shot()
endattendee)
def celebrate(Conference conf)
conf.provide_free_beers_tonight()
endattendee)
# *cough*
if obj.is_a?(Conference)
handle_conf(obj)
elsif obj.is_a?(Attendee)
handle_attendee(obj)

25. Functional API
class Attendee
def attend(conference)
def celebrate
raise if @is_attending.nil?
class Attendee
public def live(conference)
attend(conference)
celebrate
end
OOP

26. Parametrization,
cause we can!
if MYCOMPANY == true
img_path = “mycomp/imgs” + “hi.jpg”
img = image_tag(path)
section = content_for(:blog, img)
else
img_path = “/imgs” + “hi.jpg”
img = image_tag(path)
section = content_for(blog_name, img)
def render_section(path, content_name)
img_path = path + “hi.jpg”
img = image_tag(path)
section = content_for(content_name, img)
if MYCOMPANY == true
render_section(“mycomp/imgs”, :blog)
else
render_section(“img”, blog_name)

27. Dispatching hashaction =
if type == :attendee
:register
elsif type == :speaker
:wake_up
elsif type == :matz
:make_tea
# ...
actions = {
attendee: :register,
speaker: :wake_up,
matz: :make_tea,
} # Extendable!
action = actions[type] # no if!
MyActions.send(action) # no if!
“Dispatching Hash”

28. Glass on white background | Artist: N. Sutterer | 2019 | Abstract painting on vinyl | € 3299,-

29. def order_beer_for(person) when person in [:ivan, :nick] do
# do something
end

30. class Attendee::Update < Trailblazer::Operation
step :find_attendee
step :validate
step :save
fail :alert_admin
step :notify_admin
end

31. class Attendee::Update < Trailblazer::Operation
step :find_attendee
step :validate
step :save
fail :alert_admin
step :notify_admin
end
def process(…)
if find_attendee(…)
if validate(…)
if save(…)
if notify_admin(…)
else
alert_admin(…)
end
else
alert_admin(…)
end
else
alert_admin(…)
end
end

32. class Attendee::Update < Trailblazer::Operation
step :find_attendee
step :validate
step :save
fail :alert_admin
step :notify_admin
end
activity Attendee::Update
step :find_attendee
step :validate
step :save
fail :alert_admin
step :notify_admin
end

34. trace(options) if TRACING == true

37. “Trust us”

38. ...and now,
my dear friends,
let’s if together!
@apotonick