module Nokogiri::ClassResolver

Some classes in Nokogiri are namespaced as a group, for example Document, DocumentFragment, and Builder.

It’s sometimes necessary to look up the related class, e.g.:

XML::Builder → XML::Document
HTML4::Builder → HTML4::Document
HTML5::Document → HTML5::DocumentFragment

This module is included into those key classes who need to do this.

Constants

VALID_NAMESPACES: related_class restricts matching namespaces to those matching this set.

Public Instance Methods

related_class(class_name) → Class

Source

# File lib/nokogiri/class_resolver.rb, line 44
def related_class(class_name)
  klass = nil
  inspecting = self.class

  while inspecting
    namespace_path = inspecting.name.split("::")[0..-2]
    inspecting = inspecting.superclass

    next unless VALID_NAMESPACES.include?(namespace_path.last)

    related_class_name = (namespace_path << class_name).join("::")
    klass = begin
      Object.const_get(related_class_name)
    rescue NameError
      nil
    end
    break if klass
  end
  klass
end

Find a class constant within the

Some examples:

Nokogiri::XML::Document.new.related_class("DocumentFragment")
# => Nokogiri::XML::DocumentFragment
Nokogiri::HTML4::Document.new.related_class("DocumentFragment")
# => Nokogiri::HTML4::DocumentFragment

Note this will also work for subclasses that follow the same convention, e.g.:

Loofah::HTML::Document.new.related_class("DocumentFragment")
# => Loofah::HTML::DocumentFragment

And even if it’s a subclass, this will iterate through the superclasses:

class ThisIsATopLevelClass < Nokogiri::HTML4::Builder ; end
ThisIsATopLevelClass.new.related_class("Document")
# => Nokogiri::HTML4::Document