Globally scoped methods in Ruby

Intro

Just reading the Wikipedia entry on Ruby and found out this interesting bit of semantics.

Every function is a method and methods are always called on an object. Methods defined at the top level scope become members of the Object class. Since this class is an ancestor of every other class, such methods can be called on any object. They are also visible in all scopes, effectively serving as "global" procedures.

That's a pretty interesting concept—that any globally scoped methods get encapsulated in the Object class.

Globals Considered Harmful

We learned long ago that Globally accessable data is a fail. Abstraction and encapsulation give us the tools we need to properly implement information hiding.

So having it cooked into the language that any globally scoped function is just a method on the Object class is good out of the box Object Oriented behavior of which I approve.

Code Example

def globally_scoped_method
  puts "This is a globally scoped method."
end

class MyClass
  def initialize
    globally_scoped_method
  end
end

myClass = MyClass.new
# Logs: This is a globally scoped method.

It's important to note that globally_scoped_method is added as a private method of the Object class. Therefore it would be impossible to call it like so

def globally_scoped_method
  puts "This is a globally scoped method."
end

class MyClass
  def initialize
  end
end

myClass = MyClass.new
myClass.globally_scoped_method
# NoMethodError: private method `globally_scoped_method' called for #<MyClass:0x016ff23dc23832>

Published

Tags

• ruby 7
• code 21