Question

In ruby, when one defines a method in the root scope, it can be called from that scope:

def foo
  "foo"
end
foo #=> "foo"

In any other context this is not the case:

class Bar
  def foo
    "foo"
  end
  foo #=> Error: No Method `foo` for class Bar
end

What mechanism is used in setting up the main object (an instance of Object) that allows this to happen?

Answer 1

This is really special cased in Ruby. If you define methods in the global scope they get actually defined on Kernel which is included in every object by default.

Kernel is also there when no other context is defined. Since Class inherits also from Kernel methods defined on it are also in scope in class scopes.