Private Classes in Ruby (original) (raw)

Last Updated : 17 Jan, 2023

The concept of private, protected and public methods in Ruby is a bit different than it other languages like Java. In Ruby, it is all about which class the person is calling, as classes are objects in ruby.

Private Class

When a constant is declared private in Ruby, it means this constant can never be called with an explicit receiver, a private constant will be called only with an implicit receiver. So, in ruby private classes can be defined inside a class as a sub-class and declaring them into private constants, here this private class can be only accessed through the outer-class. Syntax:

private_constant: class

Below is the example of Public class:

Ruby `

by default public

class Marvel

by default public

class Guardians def Quill puts "Legendary outlaw" end def Groot puts "I am Groot" end end

by default public

class Avengers def Tony puts "I am Iron-man" end end end Marvel::Avengers.new.Tony Marvel::Guardians.new.Quill

`

Output:

I am Iron-man Legendary outlaw

In the above example as the sub-classes Guardians and Avengers are public, both implicit and explicit users have access to it.

• Check out the private class Example : Ruby `

Ruby program of accessing private class

public

class Marvel

Private

class Guardians def Quill puts "Legendary outlaw" end def Groot puts "I am Groot" end end

public

class Avengers def Tony puts "I am Iron-man" end end

making Guardians class private

private_constant :Guardians end

Marvel::Avengers.new.Tony

throws an error(NameError)

Marvel::Guardians.new.Quill

`

Output:

I am Iron-man main.rb:20:in `': private constant Marvel::Guardians referenced (NameError)

• So, here if we look at the code they aren't any access-specifier keywords to make a class as private or public, but they do exist in Ruby, but cannot deal with classes. To make a class as private we need to take the help of private_constant, here this makes any object, class or method as private which will be unavailable to access for explicit users.
• how can a private class can be accessed through the outer-class. Ruby `

Ruby program a private class accessed through the outer-class.

public

class Marvel

private

class Guardians def Quill puts "Legendary outlaw" end def Groot puts "I am Groot" end end

private

class Avengers def Tony puts "I am Iron-man" end end

outer-class method accessing private classes

def fury Guardians.new.Groot Avengers.new.Tony end private_constant :Guardians private_constant :Avengers end

calls fury method in Marvel call.

Marvel.new.fury

throws error as it is explicit accessing.

Marvel::Avengers.new.Tony

throws error as it is explicit accessing.

Marvel::Guardians.new.Quill

`

Output:

I am Groot I am Iron-man main.rb:26:in `': private constant Marvel::Avengers referenced (NameError)

• The only way to access the private class(inner-class) is by its outer-class. And private classes can only exist in the form of inner-class only. As we can see in the above code we accessed Groot and Tony (private class methods) with fury (outer class method), by creating Guardians.new and Avengers.new (private class objects) and calling the respective methods with the respective objects Guardians.new.Groot and Avengers.new.Tony (calling the methods) from fury (outer-class method). if the outer-class is private it will be inaccessible for both implicit and explicit users. Because creating an object for private class outside its class is not possible. Therefore no access.

**Note :**Outer-class can never be private.