Ruby Parameters

Key Parameter Types

def add(a, b)
  a + b
end

def greet(name = "Friend")
  puts "Hi #{name}"
end

def user(name:, age:)
  puts "#{name}, #{age}"
end

def sum(*numbers)
  numbers.sum
end

🔹 Required Parameters

Required parameters must be provided when calling a method. If you forget to pass them, Ruby raises an error. They ensure your method receives all necessary data to function correctly.

# Single parameter
def square(number)
  number * number
end

puts square(5)

# Multiple parameters
def introduce(name, age, city)
  puts "I'm #{name}, #{age} years old, from #{city}"
end

introduce("Alice", 28, "New York")

# Order matters
def subtract(a, b)
  a - b
end

puts subtract(10, 3)  # 10 - 3
puts subtract(3, 10)  # 3 - 10

🔹 Default Parameters

Default parameters provide fallback values when arguments aren't passed. This makes methods more flexible and user-friendly, allowing them to work with or without specific inputs while maintaining sensible defaults.

# Single default parameter
def greet(name = "Guest")
  puts "Welcome, #{name}!"
end

greet("Sarah")
greet

# Multiple defaults
def create_account(username, role = "user", active = true)
  puts "Account: #{username}, Role: #{role}, Active: #{active}"
end

create_account("john123")
create_account("admin456", "admin")
create_account("test789", "tester", false)

# Mix required and default
def calculate_price(amount, tax = 0.1, discount = 0)
  total = amount + (amount * tax) - discount
  puts "Total: $#{total}"
end

calculate_price(100)
calculate_price(100, 0.15)
calculate_price(100, 0.15, 10)

🔹 Keyword Parameters

Keyword parameters use names instead of position, making method calls clearer and self-documenting. They prevent errors from argument order and make code more maintainable, especially with many parameters.

# Required keyword parameters
def create_user(name:, email:, age:)
  puts "User: #{name}, Email: #{email}, Age: #{age}"
end

create_user(name: "Alice", email: "[email protected]", age: 25)
create_user(age: 30, name: "Bob", email: "[email protected]")  # Order doesn't matter

# Optional keyword parameters
def send_email(to:, subject: "No Subject", body: "")
  puts "To: #{to}"
  puts "Subject: #{subject}"
  puts "Body: #{body}"
end

send_email(to: "[email protected]")
send_email(to: "[email protected]", subject: "Hello", body: "Welcome!")

# Mix positional and keyword
def register(username, email:, password:, age: 18)
  puts "Username: #{username}, Email: #{email}, Age: #{age}"
end

register("john_doe", email: "[email protected]", password: "secret123")

🔹 Splat Operator (*)

The splat operator collects multiple arguments into an array. It's perfect when you don't know how many arguments will be passed, allowing methods to handle variable numbers of inputs elegantly.

# Variable number of arguments
def sum(*numbers)
  total = numbers.sum
  puts "Sum of #{numbers.inspect} = #{total}"
end

sum(1, 2, 3)
sum(10, 20, 30, 40, 50)
sum(5)

# Mix regular and splat parameters
def introduce(name, *hobbies)
  puts "I'm #{name}"
  puts "My hobbies: #{hobbies.join(', ')}"
end

introduce("Alice", "reading", "coding", "gaming")

# Double splat for keyword arguments
def display_info(name, **details)
  puts "Name: #{name}"
  details.each { |key, value| puts "#{key}: #{value}" }
end

display_info("Bob", age: 30, city: "NYC", job: "Developer")

🔹 Practical Examples

Real-world parameter usage demonstrates how to build flexible, reusable methods. These examples show common patterns for handling user input, calculations, and data processing in everyday Ruby programming tasks.

# Shopping cart calculator
def calculate_total(price, quantity = 1, discount: 0, tax: 0.08)
  subtotal = price * quantity
  after_discount = subtotal - (subtotal * discount)
  total = after_discount + (after_discount * tax)
  puts "Total: $#{total.round(2)}"
end

calculate_total(50, 2)
calculate_total(100, 3, discount: 0.1)
calculate_total(75, 1, discount: 0.2, tax: 0.1)

# User profile builder
def build_profile(name, age, *skills, city: "Unknown", active: true)
  puts "Profile: #{name}, #{age} years old"
  puts "Skills: #{skills.join(', ')}"
  puts "City: #{city}, Active: #{active}"
end

build_profile("John", 28, "Ruby", "JavaScript", "Python", city: "Boston")