Problem:

For whatever reason, you want to create a class named Integer and instantiate objects with that class.

Approach:

You create the class like this:

3.2.6 :001 > class Integer
3.2.6 :002 > end
 => nil

That works like a charm. Now you proceed to instantiate objects using the newly created Integer class. Boom, you run into the error below:

3.2.6 :003 > Integer.new
(irb):3:in `<main>': undefined method `new' for Integer:Class (NoMethodError)

Integer.new
       ^^^^
	from /usr/share/rvm/gems/ruby-3.2.6/gems/irb-1.15.1/exe/irb:9:in `<top (required)>'
	from /usr/share/rvm/gems/ruby-3.2.6/bin/irb:25:in `load'
	from /usr/share/rvm/gems/ruby-3.2.6/bin/irb:25:in `<main>'
	from /usr/share/rvm/gems/ruby-3.2.6/bin/ruby_executable_hooks:22:in `eval'
	from /usr/share/rvm/gems/ruby-3.2.6/bin/ruby_executable_hooks:22:in `<main>'
3.2.6 :004 >

Explanation of why we run into the error:

While this is valid ruby syntax for instantiating objects from a class, you can see we ran into a specific kind of error named a “NoMethodError”.

Ruby ships with an inbuilt class called Integer and this class doesn’t have a new method defined for it. When you try to create new objects by calling Integer.new, instead of Ruby calling the new method on your newly created Integer class, the new method is called on ruby’s inbuilt Integer class. And because this class doesn’t have a method named new defined for it, we run into the “no method error”.

<main>': undefined method `new' for Integer:Class (NoMethodError)

In simple terms, the error loosely translates to: “Hey, you called a method named new on my Integer class. But when i go through my list of methods defined for the Integer class, I can’t find this method named new.”

A simple irb check lets you know that indeed this default Integer class has no method named new defined for it.

3.2.6 :007 > Integer.methods.include?(:new)
 => false 
3.2.6 :008 >

Potential solution(s):

One solution is to consider a different name for your new class. Ideally one that doesn’t conflict with the names of inbuilt ruby classes. That could work, but what if you don’t wanna consider a different name?

In that case, you can solve the above error by wrapping your newly created class in a module. You can name that module what ever you like and use it to reference the custom Integer class when creating new objects like below:

3.2.6 :008 > module Namespace
3.2.6 :009 >   class Integer
3.2.6 :010 >   end
3.2.6 :011 > end
 => nil 
3.2.6 :012 > Namespace::Integer.new
 => #<Namespace::Integer:0x000075c9a235a098> 
3.2.6 :013 >

As you can see, with the module approach, we don’t run into any problems instantiating objects with the custom Integer class.

Bonus:

The simple irb check below confirms that the new method is available for your newly created Namespace::Integer class.

3.2.6 :013 > Namespace::Integer.methods.include?(:new)
 => true 
3.2.6 :014 >

In case you hadn’t noticed I named my module “Namespace”. This is because the act of wrapping a class in a module to prevent name collisions with another class, for example the inbuilt Integer and custom Integer classes, is referred to as Namespacing. Therefore, my module name was a subtle hint to the term used to refer to the technique I was applying to solve the problem.