Keyword arguments in Ruby

Introduction

Keyword arguments let you give names to inputs when calling a method. This makes your code easier to read and understand.

When a method needs many inputs and you want to avoid confusion about their order.

When you want to make some inputs optional with default values.

When you want to clearly show what each input means in your code.

When you want to improve code readability for others or your future self.

Syntax

Ruby

def method_name(arg1:, arg2: default_value)
  # method body
end

method_name(arg1: value1, arg2: value2)

Keyword arguments are written with a colon after the name in the method definition.

You call the method by naming each argument, like arg1: value.

Examples

This method requires both name and age as keyword arguments.

Ruby

def greet(name:, age:)
  puts "Hello, #{name}! You are #{age} years old."
end

greet(name: "Alice", age: 30)

Here, age has a default value of 18, so you can skip it when calling.

Ruby

def greet(name:, age: 18)
  puts "Hello, #{name}! You are #{age} years old."
end

greet(name: "Bob")

This method shows how to use a default value for size.

Ruby

def order(drink:, size: "medium")
  puts "You ordered a #{size} #{drink}."
end

order(drink: "coffee")

Sample Program

This program defines a method to book a flight using keyword arguments. It shows how to use default values and how to call the method with different arguments.

Ruby

def book_flight(destination:, date:, seat_class: "economy")
  puts "Booking a #{seat_class} seat to #{destination} on #{date}."
end

book_flight(destination: "Paris", date: "2024-07-01")
book_flight(destination: "Tokyo", date: "2024-08-15", seat_class: "business")

Important Notes

If you forget to provide a required keyword argument, Ruby will raise an error.

Keyword arguments improve code clarity by naming each input explicitly.

Summary

Keyword arguments let you name inputs when calling methods.

You can set default values to make some arguments optional.

This makes your code easier to read and less error-prone.