Clean Code ✨

What is Clean Code? ♻️

Where did Clean Code originate? 📘

Note

"Clean Code: A Handbook of Agile Software Craftsmanship" (2008)

— Robert C. Martin

Some signs that the code is dirty 💩

Rigidity

Note

"Business changes. Technology changes. The team changes. Team members change. The problem is not the change itself, because change will happen; the problem, in fact, is the inability to cope with change when it arrives."

— Kent Beck

Complexity

Note

"Complexity kills. Complexity destroys the developer's life. Complexity makes the product hard to plan, build, and test."

— Ray Ozzie (CTO of Microsoft)

Note

"It is harder to read the code than to write it."

— Joel Spolsky (Creator and CEO of Stack Overflow)

Fragility

Note

"If a change in requirements breaks your architecture, then your architecture is crap."

— Robert C. Martin

Note

"If you are afraid to change something, then it is poorly designed."

— Martin Fowler

Imobility

Note

"Code reuse is the Holy Grail of Software Engineering."

— Douglas Crockford

How can I clean my code? 🧹

Warning

The didactic examples are written in Ruby language to convey the idea in a simple and didactic way, but keep in mind that these Clean Code techniques work in any programming language.

DRY

Note

"Duplication is the primary enemy of a well-designed system. It represents extra work, extra risk, and unnecessary extra complexity."

— Robert C. Martin

Note

"I think one of the most valuable rules is to avoid duplication. Once and only once."

— Martin Fowler

Didactic Example 👨‍💻

def greet_morning
 puts "Good morning, Alice!"
end
def greet_afternoon
 puts "Good afternoon, Alice!"
end
def greet_evening
 puts "Good evening, Alice!"
end
greet_morning
greet_afternoon
greet_evening

def greet(day_period, name)
 puts "Good #{day_period}, #{name}!"
end
greet("morning", "Alice")
greet("afternoon", "Alice")
greet("evening", "Alice")

KISS

Note

"A difference between a smart programmer and a professional programmer is that the professional understands that clarity is what matters. 👑 Professionals use their powers for good and write code that others can understand."

— Robert C. Martin

Note

"Simple can be harder than complex. You have to work hard to get your thinking clean and simple. But it's worth it in the end, because once you get there, you can move mountains."

— Steve Jobs

Didactic Example 👨‍💻

def calculate_discount(price)
 if price > 100
 if price < 200
 discount = 10
 else
 discount = 20
 end
 else
 discount = 0
 end
 discounted_price = price - (price * discount / 100)
 return discounted_price
end
puts calculate_discount(150)
puts calculate_discount(50)
puts calculate_discount(250)

def calculate_discount(price)
 discount = case price
 when 0..100 then 0
 when 101..200 then 10
 else 20
 end
 price - (price * discount / 100)
end
puts calculate_discount(150)
puts calculate_discount(50)
puts calculate_discount(250)

YAGNI

Note

"90% of the features for the future are never used."

— Don Wells (Extreme Programming)

Note

"YAGNI applies only to the effort of making the software support future and/or hypothetical functionality; it does not apply to the effort of making the software easier to change."

— Martin Fowler

Tip

Use The Combo YAGNI → KISS → DRY

Do the Necessary → Do the Simple → Do the Unique

Didactic Example 👨‍💻

class User
 attr_accessor :name, :email, :age, :address, :phone_number
 def initialize(name, email)
 @name = name
 @email = email
 @age = nil # Unused feature
 @address = nil # Unused feature
 @phone_number = nil # Unused feature
 end
 def send_welcome_email
 puts "Welcome, #{name}! A welcome email has been sent to #{email}."
 end
end
user = User.new("Alice", "alice@example.com")
user.send_welcome_email

class User
 attr_accessor :name, :email, :age, :address, :phone_number
 def initialize(name, email)
 @name = name
 @email = email
 end
 def send_welcome_email
 puts "Welcome, #{name}! A welcome email has been sent to #{email}."
 end
end
user = User.new("Alice", "alice@example.com")
user.send_welcome_email

SRP

Note

"Functions should do one thing, do it well, and do only that."

— Robert C. Martin

Didactic Example 👨‍💻

class ReportGenerator
 def generate_report(data)
 # Process the data
 processed_data = data.map { |item| Processor.process(item) }
 # Convert data to JSON
 json_data = processed_data.to_json
 # Save the report to a file
 File.open('report.json', 'w') do |file|
 file.write(json_data)
 end
 # Send the report via email
 Email.send(data: json_data)
 end
end
data = ["a", "b", "c", "d"]
report = ReportGenerator.new
report.generate_report(data)

class ReportGenerator
 def generate_report(data)
 processed_data = process_data(data)
 json_data = convert_to_json(processed_data)
 save_report(json_data)
 send_report(json_data)
 end
 private
 def process_data(data)
 data.map { |item| Processor.process(item) }
 end
 def convert_to_json(data)
 data.to_json
 end
 def save_report(json_data)
 File.open('report.json', 'w') do |file|
 file.write(json_data)
 end
 end
 def send_report(json_data)
 Email.send(data: json_data)
 end
end
data = ["a", "b", "c", "d"]
report = ReportGenerator.new
report.generate_report(data)

Avoid Hadouken IFs

Didactic Example 👨‍💻

def process_order(order)
 if order.valid?
 if order.in_stock?
 if order.payment_successful?
 puts "Order processed successfully!"
 else
 puts "Payment failed."
 end
 else
 puts "Item is out of stock."
 end
 else
 puts "Order is invalid."
 end
end
order = Order.new
process_order(order)

def process_order(order)
 return puts "Order is invalid." unless order.valid?
 return puts "Item is out of stock." unless order.in_stock?
 return puts "Payment failed." unless order.payment_successful?
 puts "Order processed successfully!"
end
order = Order.new
process_order(order)

Avoid Negative Conditionals

Note

"Whenever possible, conditionals should be expressed as positives."

— Robert C. Martin"

Didactic Example 👨‍💻

def check_access(user)
 if !user.admin?
 if !user.premium_member?
 puts "Access denied."
 else
 puts "Access granted."
 end
 else
 puts "Access granted."
 end
end
user = User.new
check_access(user)

def check_access(user)
 if user.admin? || user.premium_member?
 puts "Access granted."
 else
 puts "Access denied."
 end
end
user = User.new
check_access(user)

Encapsulate Conditionals

Note

"Boolean logic is hard enough to understand without having to see it in the context of an if or while statement. Extract functions that explain the intent of the conditional."

— Robert C. Martin"

def check_availability(user)
 if user.age > 18 && !user.has_children? && (user.premium_member? || user.has_coupon?)
 puts "User is available for the offer."
 else
 puts "User is not available for the offer."
 end
end
user = User.new
check_availability(user)

def check_availability(user)
 if available?(user)
 puts "User is available for the offer."
 else
 puts "User is not available for the offer."
 end
end
private
def available?(user)
 return false if user.age <= 18
 return false if user.has_children?
 return true if user.premium_member?
 return true if user.has_coupon?
 false
end
user = User.new
check_availability(user)

Avoid Flag Arguments

Note

"Flag arguments are ugly. Passing a boolean into a function is a truly terrible practice."

— Robert C. Martin

Didactic Example 👨‍💻

def greet(name, formal)
 if formal
 puts "Good evening, #{name}."
 else
 puts "Hi, #{name}!"
 end
end
greet("Alice", true)
greet("Bob", false)

def greet(name, formality)
 case formality
 when "formal"
 puts "Good evening, #{name}."
 when "informal"
 puts "Hi, #{name}!"
 end
end
greet("Alice", "formal")
greet("Bob", "informal")

Avoid Comments

Note

"Don’t use a comment when you can use a function or a variable."

— Robert C. Martin

Note

"When you feel the need to write a comment, first try to refactor the code so that any comment becomes superfluous."

— Martin Fowler

Didactic Example 👨‍💻

class Calculator
 def calculate_area(radius)
 # Calculate the area of a circle
 area = Math::PI * radius ** 2
 # Round the area to two decimal places
 area = area.round(2)
 area
 end
end
calculator = Calculator.new
puts calculator.calculate_area(5) # Outputs: 78.54

class Calculator
 def calculate_area(radius)
 area = circle_area(radius)
 area = area.round(2)
 area
 end
 private
 def circle_area(radius)
 Math::PI * radius ** 2
 end
end
calculator = Calculator.new
puts calculator.calculate_area(5) # Outputs: 78.54

Good Nomenclatures

Note

"You should name a variable using the same care with which you name a first-born child."

— Robert C. Martin

Note

"Any organization that designs a system will produce a design whose structure is a copy of the organization’s communication structure."

— Robert C. Martin

Didactic Example 👨‍💻

def fact(n)
 if n <= 1
 1
 else
 n * fact(n - 1)
 end
end
x = 5
y = fact(x)
puts y # Outputs: 120

def factorial(number)
 if number <= 1
 1
 else
 number * factorial(number - 1)
 end
end
number = 5
result = factorial(number)
puts result # Outputs: 120

Use Vertical Formatting

Note

"Programs must be written for people to read, and only incidentally for machines to execute."

— Hal Abelson and Jerry Sussman

Note

"Programming is the art of telling another human being what one wants the computer to do."

— Donald Knuth

Didactic Example 👨‍💻

class Calculator
 def add(a, b)
 a + b
 end
 def multiply(a, b)
 a * b
 end
 def calculate(a, b)
 sum = add(a, b)
 difference = subtract(a, b)
 product = multiply(a, b)
 quotient = divide(a, b)
 [sum, difference, product, quotient]
 end
 def divide(a, b)
 a / b
 end
 def subtract(a, b)
 a - b
 end
end
calculator = Calculator.new
result = calculator.calculate(10, 5)
puts result # 15, 5, 50, 2

class Calculator
 def calculate(a, b)
 sum = add(a, b)
 difference = subtract(a, b)
 product = multiply(a, b)
 quotient = divide(a, b)
 [sum, difference, product, quotient]
 end
 def add(a, b)
 a + b
 end
 def subtract(a, b)
 a - b
 end
 def multiply(a, b)
 a * b
 end
 def divide(a, b)
 a / b
 end
end
calculator = Calculator.new
result = calculator.calculate(10, 5)
puts result # 15, 5, 50, 2

Delete Code > Create Code

Note

"One of my most productive days was when I threw away 1,000 lines of code."

— Ken Thompson

Note

"Code, like poetry, should be short and concise."

— Santosh Kalwar

Note

"Measuring programming progress by lines of code is like measuring aircraft building progress by weight."

— Bill Gates

Didactic Example 👨‍💻

class NotificationService
 def send_notification(user, message)
 if user.email_notifications_enabled
 send_email(user.email, message)
 else
 puts "Email notifications are disabled for #{user.name}."
 end
 if user.sms_notifications_enabled
 send_sms(user.phone_number, message)
 else
 puts "SMS notifications are disabled for #{user.name}."
 end
 end
 private
 def send_email(email, message)
 # Code to send email
 puts "Email sent to #{email}: #{message}"
 end
 def send_sms(phone_number, message)
 # Code to send SMS
 puts "SMS sent to #{phone_number}: #{message}"
 end
end
class User
 attr_accessor :name, :email, :phone_number, :email_notifications_enabled, :sms_notifications_enabled
 def initialize(name, email, phone_number)
 @name = name
 @email = email
 @phone_number = phone_number
 @email_notifications_enabled = false
 @sms_notifications_enabled = false
 end
end
# Usage
user = User.new("Alice", "alice@example.com", "123-456-7890")
user.email_notifications_enabled = true
user.sms_notifications_enabled = true
service = NotificationService.new
service.send_notification(user, "Your order has been shipped.")

class NotificationService
 def send_notification(user, message)
 send_email(user.email, message)
 send_sms(user.phone_number, message)
 end
 private
 def send_email(email, message)
 # Code to send email
 puts "Email sent to #{email}: #{message}"
 end
 def send_sms(phone_number, message)
 # Code to send SMS
 puts "SMS sent to #{phone_number}: #{message}"
 end
end
class User
 attr_accessor :name, :email, :phone_number
 def initialize(name, email, phone_number)
 @name = name
 @email = email
 @phone_number = phone_number
 end
end
# Usage
user = User.new("Alice", "alice@example.com", "123-456-7890")
service = NotificationService.new
service.send_notification(user, "Your order has been shipped.")

Boy Scout Rule

Note

"Programming is a social activity."

— Robert C. Martin

Note

"If we all checked in our code a little cleaner than when we checked it out, the code simply could not rot."

— Robert C. Martin

Didactic Example 👨‍💻

def print_user_info(user)
 puts "Name: " + user[:name]
 puts "Email: " + user[:email]
 if user[:age] != nil
 puts "Age: " + user[:age].to_s
 end
end
user = { name: "Alice", email: "alice@example.com", age: 30 }
print_user_info(user)

def print_user_info(user)
 puts "Name: #{user[:name]}"
 puts "Email: #{user[:email]}"
 puts "Age: #{user[:age]}" if user[:age]
end
user = { name: "Alice", email: "alice@example.com", age: 30 }
print_user_info(user)

Performance vs. Clarity ⚖️

Warning

"Programmers waste an enormous amount of time thinking or worrying about the speed of non-critical parts of their programs, and these attempts at efficiency have a strong negative impact when considering debugging and maintenance. We should forget about small efficiencies about 97% of the time: premature optimization is the root of all evil."

— Donald Knuth

Warning

"I asked a programmer why he wrote the code in one line instead of another approach that would better express the intent. His response was, 'This one is faster.' OK, it turns out that his code runs a picosecond (about 0.35 ps, to be precise) faster than what I proposed. And it’s triggered by a user's click on a button and executed only once. An absolutely insignificant time gain led to writing less readable code. Never do that: use the code that best expresses your intent for the next human who reads it, unless you really (really) need the execution time gain."

— Someone on Quora

Tip

"Make it work → Make it right (Clean Code) → Make it fast."

— Kent Beck

Conclusion 👨‍⚖️

Tip

"A good architecture makes the system easy to understand, easy to develop, easy to maintain, and easy to deploy. The ultimate goal is to minimize the lifetime cost of the system and maximize developer productivity."

— Robert C. Martin

References 📚

Slides 🖼️

Contact 📞