module ActiveSupport::Inflector

unknown.
NameError is raised when the name is not in CamelCase or the constant is

end
"C".constantize # => 'outside', same as ::C
C # => 'inside'
C = 'inside'
module M
C = 'outside'

it starts with "::" or not. No lexical context is taken into account:
The name is assumed to be the one of a top-level constant, no matter whether

"Test::Unit".constantize # => Test::Unit
"Module".constantize # => Module

Tries to find a constant with the name specified in the argument string:

def constantize(camel_cased_word)
  names = camel_cased_word.split('::')
  names.shift if names.empty? || names.first.empty?
  constant = Object
  names.each do |name|
    constant = constant.const_defined?(name) ? constant.const_get(name) : constant.const_missing(name)
  end
  constant
end