A Brewer's Guide to Filtering out Complexity and Churn (RailsConf 2023 Edition)

Alan Ridlehoover & Fito von Zastrow
RailsConf 2023
The Coffee
Machine Talk
A Brewer’s Guide to Filtering out
Complexity and Churn

View Slide

PRONOUNS
he/him/his
HOMETOWN
Asunción 
RUBY EXPERIENCE
12 years
FAVORITE COFFEE
Ghirardelli Dark
Chocolate Mocha
PRONOUNS
he/him/his
HOMETOWN
Seattle 
RUBY EXPERIENCE
12 years
FAVORITE COFFEE
New Orleans Cold
Brew w/ Chicory

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🤲

View Slide

View Slide

👍

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How did we get here?
How complexity sneaks into a code base.

View Slide

class CoffeeMachine

def vend

dispense_cup

heat_water

prepare_grounds

dispense_water

dispose_of_grounds

end

end
☕ Story: As a patron, I want coffee

View Slide

☕ Story: As a patron, I want tea
class CoffeeMachine

def vend(drink: :coffee)

if drink == :coffee

dispense_cup

heat_water

prepare_grounds

dispense_water

dispose_of_grounds

elsif drink == :tea

dispense_cup

heat_water

dispense_tea_bag

dispense_water

end

end

end

View Slide

☕ Refactor: DRY up the code
class CoffeeMachine


dispense_cup

heat_water

if drink == :coffee

prepare_grounds

elsif drink == :tea

dispense_tea_bag

end

dispense_water

dispose_of_grounds if drink == :coffee

end

end

View Slide

☕ Story: As a patron, I want sweetener
class CoffeeMachine

def vend(drink: :coffee, options: {})

dispense_cup

heat_water

if drink == :coffee

prepare_grounds

elsif drink == :tea

dispense_tea_bag

end

dispense_water

dispense_sweetener if options[:sweet]


end

end

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class CoffeeMachine


dispense_cup

heat_water

if drink == :coffee

prepare_grounds

elsif drink == :tea

dispense_tea_bag

end

dispense_water


dispense_cream if options[:creamy]


end

end

☕ Story: As a patron, I want cream

View Slide

☕ Story: As a patron, I want cocoa
class CoffeeMachine


dispense_cup

heat_water

if drink == :coffee

prepare_grounds

elsif drink == :tea

dispense_tea_bag

elsif drink == :cocoa

dispense_cocoa_mix

end

dispense_water

unless drink == :cocoa


dispense_creamer if options[:creamy]

end


end

end

View Slide

☕ Story: As a patron, I want whipped cream
class CoffeeMachine


dispense_cup

heat_water

if drink == :coffee

prepare_grounds

elsif drink == :tea

dispense_tea_bag


dispense_cocoa_mix

end

dispense_water




end

unless drink == :tea

dispense_whipped_cream if options[:fluffy]

end


end

end

View Slide

class CoffeeMachine


dispense_cup

heat_water

if drink == :coffee

prepare_grounds

elsif drink == :tea

dispense_tea_bag


dispense_cocoa_mix

end

dispense_water




end



end


end

end
☕ 7 commits: 9 conditionals
1
2
3
4 5
6
7 8
9

View Slide

Do you smell that?
How to recognize the problem before it
becomes painful and frustrating.
Rules by Sandi Metz Flog by Ryan Davis

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Score of Means

- - - - - - - - - - - - - - - - - - - - - - - - -

0-10 Awesome

11-20 Good enough

21-40 Might need refactoring

41-60 Possible to justify

61-100 Danger

100-200 Whoop, whoop, whoop

200 + Someone please think of the children

(note: these are scores for an individual method)

What's a good
fl
og score? by Jake Scruggs
☕ Measuring complexity with the flog gem

View Slide

☕ Story: As a patron, I want coffee
class CoffeeMachine

def vend

dispense_cup

heat_water

prepare_grounds

dispense_water

dispose_of_grounds

end

end
Churn

1
Complexity

5.5
10
20
30
25
15
5
0

View Slide

class CoffeeMachine


if drink == :coffee

dispense_cup

heat_water

prepare_grounds

dispense_water

dispose_of_grounds

elsif drink == :tea

dispense_cup

dispense_tea_bag

heat_water

dispense_water

end

end

end
Churn

2
Complexity

14.6
10
20
30
25
15
5
0
☕ Story: As a patron, I want tea

View Slide

☕ Refactor: DRY up the code
class CoffeeMachine


dispense_cup

heat_water

if drink == :coffee

prepare_grounds

elsif drink == :tea

dispense_tea_bag

end

dispense_water


end

end

Churn

3
Complexity

10.9
10
20
30
25
15
5
0

View Slide

☕ Story: As a patron, I want sweetener
class CoffeeMachine


dispense_cup

heat_water

if drink == :coffee

prepare_grounds

elsif drink == :tea

dispense_tea_bag

end

dispense_water



end

end

Churn

4
Complexity

13.5
10
20
30
25
15
5
0

View Slide

☕ Story: As a patron, I want cream
class CoffeeMachine


dispense_cup

heat_water

if drink == :coffee

prepare_grounds

elsif drink == :tea

dispense_tea_bag

end

dispense_water




end

end

Churn

5
Complexity

16.0
10
20
30
25
15
5
0

View Slide

☕ Story: As a patron, I want cocoa
class CoffeeMachine


dispense_cup

heat_water

if drink == :coffee

prepare_grounds

elsif drink == :tea

dispense_tea_bag


dispense_cocoa_mix

end

dispense_water




end


end

end

Churn

6
Complexity

21.3
10
20
30
25
15
5
0

View Slide

☕ Story: As a patron, I want whipped cream
class CoffeeMachine


dispense_cup

heat_water

if drink == :coffee

prepare_grounds

elsif drink == :tea

dispense_tea_bag


dispense_cocoa_mix

end

dispense_water




end



end


end

end

Churn

7
Complexity

25.5
10
20
30
25
15
5
0

View Slide

☕ CoffeeMachine pain index over time
class CoffeeMachine


dispense_cup

heat_water

if drink == :coffee

prepare_grounds

elsif drink == :tea

dispense_tea_bag


dispense_cocoa_mix

end

dispense_water




end



end


end

end

Churn

7
Complexity

25.5
10
20
30
25
15
5
0

View Slide

☕ CoffeeMachine pain index over time
class CoffeeMachine


dispense_cup

heat_water

if drink == :coffee

prepare_grounds

elsif drink == :tea

dispense_tea_bag


dispense_cocoa_mix

end

dispense_water




end



end


end

end

Churn

7
Complexity

25.5
10
20
30
25
15
5
0
Complexity

25.5

View Slide

Can we turn it around?
How to
fi
lter out complexity and churn.

View Slide

☕ Refactor: Rehydrate to see missing abstractions
class CoffeeMachine


dispense_cup

heat_water

if drink == :coffee

prepare_grounds

elsif drink == :tea

dispense_tea_bag


dispense_cocoa_mix

end

dispense_water




end



end


end

end

View Slide


View Slide

class CoffeeMachine


dispense_cup

heat_water

if drink == :coffee

prepare_grounds

elsif drink == :tea

dispense_tea_bag


dispense_cocoa_mix

end

dispense_water




end



end


end

end

View Slide

class CoffeeMachine


if drink == :coffee

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

elsif drink == :tea

dispense_cup

heat_water

dispense_tea_bag

dispense_water




dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end

end

View Slide

☕ Refactor: Extract polymorphic objects
class CoffeeMachine


if drink == :coffee

Coffee.new(options: options).prepare

elsif drink == :tea

Tea.new(options: options).prepare


Cocoa.new(options: options).prepare

end

end

end

class Coffee < Beverage

def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water

dispense_sweetener if sweet?

dispense_cream if creamy?

dispense_whipped_cream if fluffy?

dispose_of_grounds

end

end

 
class Tea < Beverage

def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end

 
class Cocoa < Beverage

def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end

View Slide

☕ Refactor: Extract polymorphic objects
class CoffeeMachine


BeverageFactory.build(drink, options).prepare

end

end

class BeverageFactory

def self.build(beverage, options)

if beverage == :coffee

Coffee.new(options)

elsif beverage == :tea

Tea.new(options)

elsif beverage == :cocoa

Cocoa.new(options)

end

end

end


def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

end

end

 

def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end

 

def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end

View Slide

☕ Refactor: Introduce the NullObject pattern
class CoffeeMachine



end

end



if beverage == :coffee

Coffee.new(options)

elsif beverage == :tea

Tea.new(options)

elsif beverage == :cocoa

Cocoa.new(options)

else

NullBeverage.new(options)

end

end

end

class NullBeverage < Beverage

def prepare

# no-op

end

end


def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

end

end

 

def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end

 

def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end

View Slide

☕ Refactor: Use convention to prevent churn
class CoffeeMachine



end

end



klass = beverage.capitalize

if Module.const_defined?(klass)

Module.const_get(klass).new(options)

else


end

end

end


def prepare

# no-op

end

end


def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

end

end

 

def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end

 

def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end

View Slide

Self Registration
How to create an open/closed factory class.
🚧

View Slide

☕ Refactor: Introduce self-registration
class CoffeeMachine



end

end



klass = beverage.capitalize

if Module.const_defined?(klass)

Module.const_get(klass).new(options)

else


end

end

end


def prepare

# no-op

end

end


def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

end

end

 

def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end

def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end

View Slide

class CoffeeMachine



end

end


def self.build(key, options)

beverage_class(key).new(options)

end

def self.register(key, klass)

beverages[key] = klass

end

def self.beverage_class(key)

beverages[key] || NullBeverage

end

def self.beverages

@beverages ||= {}

end

end


def prepare

# no-op

end

end


BeverageFactory.register(:coffee, self)

def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

end

end

 

BeverageFactory.register(:tea, self)

def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end

BeverageFactory.register(:cocoa, self)

def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end

View Slide



def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

end

end

 


def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end


def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end

class CoffeeMachine



end

end




end



end



end

def self.beverages

@beverages ||= {}

end

end


def prepare

# no-op

end

end

View Slide

class CoffeeMachine



end

end




end



end



end

def self.beverages

@beverages ||= {}

end

end


def prepare

# no-op

end

end


 
def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

end

end

 


def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end


def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end


View Slide

class CoffeeMachine



end

end




end



end



end

def self.beverages

@beverages ||= {}

end

end


def prepare

# no-op

end

end

# {

# :coffee => Coffee,
 
# :tea => Tea,

# :cocoa => Cocoa

# )



def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

end

end

 


def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end


def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end


View Slide

class CoffeeMachine



end

end




end



end



end

def self.beverages

@beverages ||= {}

end

end


def prepare

# no-op

end

end



def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

end

end

 


def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end


def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end


View Slide

class CoffeeMachine



end

end




end



end



end

def self.beverages

@beverages ||= {}

end

end


def prepare

# no-op

end

end


prepares :coffee

def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

end

end

 

prepares :tea

def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end

class Beverage

def self.prepares(key)

BeverageFactory.register(key, self)

end

# initializer & other shared code

end


prepares :cocoa

def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end


View Slide

class CoffeeMachine



end

end




end



end



end

def self.beverages

@beverages ||= {}

end

end


def prepare

# no-op

end

end


prepares :coffee

def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

end

end

 

prepares :tea

def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end

class Beverage



end


end


prepares :cocoa

def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end

View Slide

https://github.com/
fi
rst-try-software/manufacturable
☕ Manufacturable: A gem for self-registration

View Slide

Did that work?
Were we able to reduce the complexity?

View Slide

☕ Complexity of the CoffeeMachine class over time
Rehydrate
Extract Classes
Introduce Factory
Whipped Cream
Cocoa
Cream
Sweetener
DRY
Tea
Co
ff
ee
10
20
30
25
15
5
0
40
35

View Slide

☕ Complexity of the CoffeeMachine class over time
Rehydrate
Extract Classes
Introduce Factory 
and self-registration
Whipped Cream
Cocoa
Cream
Sweetener
DRY
Tea
Co
ff
ee
10
20
30
25
15
5
0
40
35

View Slide

☕ Complexity of the application
Class Churn Complexity

--------------------- ----- ----------

CoffeeMachine 10 3.9

BeverageFactory 3 1.8

Beverage 2 2.2
 
Coffee 1 16.6

Tea 1 11.8

Cocoa 1 8.1

NullBeverage 1 0.0

View Slide

Now, who wants ?
How to add functionality without modifying existing
fi
les.

View Slide

class CoffeeMachine



end

end




end



end



end

def self.beverages

@beverages ||= {}

end

end


def prepare

# no-op

end

end


prepares :coffee

def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

end

end

 

prepares :tea

def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end

class Beverage



end


end


prepares :cocoa

def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end

View Slide

class CoffeeMachine



end

end




end



end



end

def self.beverages

@beverages ||= {}

end

end


def prepare

# no-op

end

end


prepares :coffee

def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

end

end

 

prepares :tea

def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end

class Beverage



end


end


prepares :cocoa

def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end

class TomatoSoup < Beverage

prepares :tomato_soup

def prepare

dispense_cup

heat_water

dispense_condensed_soup

dispense_water

dispense_croutons if crunchy?

dispense_hot_sauce if spicy?

end

end

View Slide

class CoffeeMachine



end

end




end



end



end

def self.beverages

@beverages ||= {}

end

end


def prepare

# no-op

end

end


prepares :coffee

def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

end

end

 

prepares :tea

def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end

class Beverage



end


end


prepares :cocoa

def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end

View Slide

class CoffeeMachine



end

end




end



end



end

def self.beverages

@beverages ||= {}

end

end


def prepare

# no-op

end

end


prepares :coffee

def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

end

end

 

prepares :tea

def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end

class Beverage



end


end


prepares :cocoa

def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end



def prepare

dispense_cup

heat_water


dispense_water



end

end

View Slide

class CoffeeMachine



end

end




end



end



end

def self.beverages

@beverages ||= {}

end

end


def prepare

# no-op

end

end


prepares :coffee

def prepare

dispense_cup

heat_water

prepare_grounds

dispense_water




dispose_of_grounds

end

end

 

prepares :tea

def prepare

dispense_cup

heat_water

dispense_tea_bag

dispense_water



end

end

class Beverage



end


end


prepares :cocoa

def prepare

dispense_cup

heat_water

dispense_cocoa_mix

dispense_water


end

end



def prepare

dispense_cup

heat_water


dispense_water



end

end

class AppleCider < Beverage

prepares :apple_cider

def prepare

dispense_cup

heat_water

dispense_cider_mix

dispense_water

dispense_cinnamon_stick

end

end

View Slide

Yeah, but does it scale?
How to apply this to a large, complicated code base.

View Slide

☕ Plotting complexity vs. churn
Churn
Complexity
Getting Empirical about Refactoring by Michael Feathers

View Slide

Churn
Complexity
Pain Free

View Slide

Pain Free
Painful
Churn
Complexity

View Slide

Pain Free
Painful
Churn
Complexity
Configuration?

View Slide

Pain Free
Painful
Churn
Complexity
Configuration?
Omega Mess?
Go Ahead, Make a Mess by Sandi Metz

View Slide

Churn
Complexity

View Slide

Conclusion
A Brewer’s Guide to Filtering out Complexity and Churn

View Slide

Take Aways

View Slide

Take Aways
Complexity will sneak into your code.
• Happens one commit at a time
• Conditionals and DRY are often the culprits

View Slide

Take Aways
You can recognize complexity before it becomes painful.
• Keep methods short
• Watch complexity
• Pay attention to how it feels

View Slide

Take Aways
You can recognize complexity before it becomes painful.
• Keep methods short
• Watch complexity
• Pay attention to how it feels
And, you can back away from painful complexity.
• Polymorphism and factories are your friends
• Overly DRY code can hide abstractions and couple algorithms in dangerous ways
• Self-registration can take you across the no-churn
fi
nish line

View Slide

Homework

View Slide

Homework
What is the average method complexity for your application?
• Use the Flog gem to measure complexity

View Slide

Homework
What is the
fi
le with the most churn in your application?
• Use the Churn gem to measure churn

View Slide

Homework
What is the
fi
Which class in your application needs the most attention?
• Use the Ruby Critic gem to plot complexity vs. churn
• Look for the
fi
le with the highest complexity and churn

View Slide

Homework
What is the
fi
Which class in your application needs the most attention?
• Use the Ruby Critic gem to plot complexity vs. churn
• Look for the
fi
le with the highest complexity and churn
Where might you use self-registration in your code?
• Play with the technique
fi
rst to get a feel for it
• Look at the Manufacturable gem for industrial-scale self-registration

View Slide

Get in touch!
EMAIL
fi
[email protected] 
GITHUB
@Fito
TWITTER
@
fi
to.vonzastrow
MASTODON
@[email protected]
EMAIL
[email protected]
GITHUB
@aridlehoover 
TWITTER
@aridlehoover
MASTODON
@[email protected]
BLOG
the.codegardener.com
GITHUB REPO
https://github.com/
fi
rst-try-software/co
ff
ee

View Slide

Ruby Flog
Ruby Flog
Ruby Flog 
 
A VS Code extension that puts
fl
og scores in your status bar…

View Slide

We are the largest Rails shop you’ve never heard of.
We build Internet machines for co
ff
ee lovers.
Our 16 year old, 1.5 million line monolith supports:
• A multi-billion dollar business
• Billions of requests per day
Our team is solving hard problems related to:
• Code complexity
• Rails at scale
https://meraki.cisco.com/jobs

View Slide

Thanks for coming!
Sandi Metz
• Practical Object Oriented Design in Ruby (book)

• 99 Bottles of OOP (book) (sample on the topic of measuring complexity)

• Rules: https://youtu.be/npOGOmkxuio

• Go Ahead, Make a Mess: https://youtu.be/mpA2F1In41w

Ryan Davis
• Flog: https://github.com/seattlerb/
fl
og
Jake Scruggs
• https://jakescruggs.blogspot.com/2008/08/whats-good-
fl
og-score.html

Michael Feathers
• Working E
ff
ectively with Legacy Code (book)

• https://www.agileconnection.com/article/getting-empirical-about-refactoring

Alan Ridlehoover & Fito von Zastrow
• Manufacturable: https://github.com/
fi
rst-try-software/manufacturable

• Ruby Flog: https://marketplace.visualstudio.com/items?itemName=
fi
rst-try-software.ruby-
fl
og

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A Brewer's Guide to Filtering out Complexity and Churn (RailsConf 2023 Edition)

A Brewer's Guide to Filtering out Complexity and Churn (RailsConf 2023 Edition)

Alan Ridlehoover
PRO

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A Brewer's Guide to Filtering out Complexity and Churn (RailsConf 2023 Edition)

A Brewer's Guide to Filtering out Complexity and Churn (RailsConf 2023 Edition)

Alan Ridlehoover PRO

More Decks by Alan Ridlehoover

Other Decks in Programming

Featured

Transcript

Alan Ridlehoover
PRO