Ruby Public Method

last modified April 27, 2025

This tutorial explains how to use Ruby’s public method. Public methods form the interface of your classes and are accessible from anywhere.

The public keyword in Ruby defines methods that can be called from anywhere in your program. By default, all methods in Ruby are public except when explicitly marked otherwise.

Public methods represent the external interface of your classes. They should be stable and well-documented as other code depends on them.

Basic Public Method Example

This simple example demonstrates a basic public method in a Ruby class. Public methods can be called on instances of the class.

basic_public.rb

class Greeter def say_hello puts “Hello, world!” end end

greeter = Greeter.new greeter.say_hello

The say_hello method is public by default. We can call it on any Greeter instance. Public methods form the class’s public API.

Explicit Public Declaration

Ruby allows explicitly declaring methods as public using the public keyword. This is useful after defining private or protected methods.

explicit_public.rb

class Calculator def add(a, b) a + b end

private

def secret_method puts “This is private” end

public

def multiply(a, b) a * b end end

calc = Calculator.new puts calc.add(2, 3) puts calc.multiply(2, 3)

The multiply method is explicitly made public after the private section. Both add and multiply are accessible.

Public Class Methods

Class methods can also be public. These are called on the class itself rather than instances. The self. prefix defines class methods.

public_class_method.rb

class Logger def self.log(message) puts “[LOG] #{message}” end

def self.public_log(message) puts “[PUBLIC] #{message}” end

private_class_method :log end

Logger.public_log(“System started”)

Only public_log is accessible here. We made log private using private_class_method. Public class methods are often used for utility functions.

Public Methods in Modules

Modules can define public methods that become available to classes that include them. These methods become part of the including class’s public interface.

module_public.rb

module Printable def print_info puts “Information: #{info}” end

private

def info “Sample data” end end

class Document include Printable end

doc = Document.new doc.print_info

The print_info method is public and available on Document instances. The private info method is only accessible within the module.

Public Accessor Methods

Ruby provides shortcuts for creating public getter and setter methods. These are commonly used to expose instance variables.

accessor_methods.rb

class Person attr_reader :name attr_writer :age attr_accessor :occupation

def initialize(name, age) @name = name @age = age end

def display puts “#{@name}, #{@age}, #{@occupation}” end end

person = Person.new(“John”, 30) person.occupation = “Developer” puts person.name person.display

attr_reader creates a public getter, attr_writer a public setter, and attr_accessor both. These are all public methods.

Public Method Overriding

Public methods can be overridden in subclasses. This allows modifying or extending behavior while maintaining the same interface.

method_override.rb

class Animal def speak puts “Animal sound” end end

class Dog < Animal def speak puts “Woof!” end end

class Cat < Animal def speak super puts “Meow!” end end

Dog.new.speak Cat.new.speak

Both Dog and Cat override the public speak method. Cat calls the parent implementation using super.

Public Method Aliasing

Ruby allows creating aliases for public methods. This is useful when you want to provide alternative names for methods.

method_alias.rb

class StringFormatter def format_text(text) text.upcase end

alias :upcase_text :format_text alias_method :uc_text, :format_text end

formatter = StringFormatter.new puts formatter.format_text(“hello”) puts formatter.upcase_text(“world”) puts formatter.uc_text(“ruby”)

Both alias and alias_method create new names for the public method. All aliases remain public and can be called interchangeably.

Source

Ruby Visibility Documentation

This tutorial covered Ruby’s public methods with practical examples showing declaration, access control, and common usage patterns.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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