Ruby, how to reference Root namespace?

Question

When I have a module like this:

module MyModule
  class MyClass
  end
end

I can access/modify MyModule referencing it:

MyModule.const_set("MY_CONSTANT", "value")

But what about the Root namespace, the :: one?, I'm looking for something like:

::.const_set("MY_CONSTANT", "value")

The const_set thing is just an example, please don't try to solve this concrete situation but the way of actually making reference to the Root namespace

Answer 1

What is the root object? If you mean main object, you can't set constant at this level:

TOPLEVEL_BINDING.eval('self').const_set("MY_CONSTANT", "value")
# NoMethodError: undefined method `const_set' for main:Object
#   from (irb):71
#   from /home/malo/.rvm/rubies/ruby-2.1.0/bin/irb:11:in `<main>'

If you mean Object object, do as follows:

Object.const_set("MY_CONSTANT", "value")
# => "value"

then you can use at the main, or at any other level:

::MY_CONSTANT
# => "value"

Adding another confirmation

We can set a constant using Kernel or using Object and in both cases the constant will be accessible from the root namespace:

Kernel.const_set("KERNEL_CONSTANT", "value")
Object.const_set("OBJECT_CONSTANT", "value")

puts !!(defined? ::KERNEL_CONSTANT) # => true
puts !!(defined? ::OBJECT_CONSTANT) # => true

But if we set a constant in the root namespace this constant is actually set in Object and not in Kernel:

::ROOT_CONSTANT = "value"

puts !!(defined? Object::ROOT_CONSTANT) # => true
puts !!(defined? Kernel::ROOT_CONSTANT) # => false