Methods

Methods

Define methods with the def keyword. Give them a name and you're off:

def greet
  "Hello, world!"
end

greet  # => "Hello, world!"

Parameters can have default values. If the caller doesn't pass anything, the default kicks in:

def greet(name = "stranger")
  "Hello, #{name}!"
end

greet("Alice")  # => "Hello, Alice!"
greet           # => "Hello, stranger!"

Splat arguments let you accept any number of arguments as an array:

def sum(*numbers)
  numbers.reduce(0, :+)
end

sum(1, 2, 3)     # => 6
sum(10, 20, 30)  # => 60

Keyword arguments make your method calls self-documenting. The caller knows exactly what each value means:

def create_user(name:, age:, role: "viewer")
  "#{name}, #{age}, #{role}"
end

create_user(name: "Alice", age: 30, role: "admin")

Ruby returns the value of the last expression automatically. Use return only when you need to exit early:

def classify(number)
  return "zero" if number == 0
  number > 0 ? "positive" : "negative"
end

You can alias a method with alias to give it a second name:

def say_hello
  "hello"
end

alias greeting say_hello
greeting  # => "hello"

Remember: in Ruby, methods are just messages you send to objects. When you call 42.odd?, you're sending the odd? message to the integer 42. That's the whole philosophy.