Ruby module given arguments calls a method?_问答_开发者

Ruby module given arguments calls a method?

开发者 https://www.devze.com 2023-03-24 13:17 出处：网络

I\'m confused about what\'s going on in the Nokogiri docs. As far as I can tell, if require \'n开发者_C百科okogiri\'

相关专题：ruby

I'm confused about what's going on in the Nokogiri docs.

As far as I can tell, if

require 'n开发者_C百科okogiri'
some_html = "<html><body><h1>Mr. Belvedere Fan Club</h1></body></html>"

then these three lines do the same thing:

html_doc = Nokogiri::HTML::Document.parse(some_html)
html_doc = Nokogiri::HTML.parse(some_html)
html_doc = Nokogiri::HTML(some_html)

The second is just a convenience method for the first. But to my non-Ruby eyes, the third looks like it's passing an argument to a module, not a method. I realize that Ruby has constructors, but I thought they took the form Class.new, not Module(args). What's going on here?

It's just syntax sugar, look at the Nokogiri::HTML module definition:

module Nokogiri
  class << self
    ###
    # Parse HTML.  Convenience method for Nokogiri::HTML::Document.parse
    def HTML thing, url = nil, encoding = nil, options = XML::ParseOptions::DEFAULT_HTML, &block
      Nokogiri::HTML::Document.parse(thing, url, encoding, options, &block)
    end
  end

  module HTML
    class << self
      ###
      # Parse HTML.  Convenience method for Nokogiri::HTML::Document.parse
      def parse thing, url = nil, encoding = nil, options = XML::ParseOptions::DEFAULT_HTML, &block
        Document.parse(thing, url, encoding, options, &block)
      end

      ####
      # Parse a fragment from +string+ in to a NodeSet.
      def fragment string, encoding = nil
        HTML::DocumentFragment.parse string, encoding
      end
    end

    # Instance of Nokogiri::HTML::EntityLookup
    NamedCharacters = EntityLookup.new
  end
end

First, they define a class method at the Nokogiri module called HTML (yes, Ruby allows you to do that), then they define the module Nokogiri::HTML and in there they define the class method parse.

Most people don't know but the :: operator can also be used to perform method calls: