使用builder創建XML

builder安裝方法：

gem install builder

require 'builder'   x = Builder::XmlMarkup.new(:target => $stdout, :indent => 1) #":target =＞$stdout"參數：指示輸出內容將被寫向標準輸出控制臺 #":indent =＞1"參數：XML輸出形式將被縮進一個空格字符x.instruct! :xml,:version =>'1.1',:encoding => 'gb2312' x.comment! "書本信息"  x.library("shelf" => "Recent Acquisitions") { x.section("name" => "ruby"){ x.book("isbn" => "0672310001"){ x.title "Programming Ruby"  x.author "Yukihiro " x.description "Programming Ruby - The Pragmatic Programmer's Guide" } } } 

p x #打印XML

Ruby創建XML輸出結果：

< ?xml version="1.1" encoding="gb2312"?> < !-- 書本信息 --> < library shelf="Recent Acquisitions"> < section name="ruby"> < book isbn="0672310001"> < title>Programming Ruby< /title> < author>Yukihiro < /author> < description>Programming Ruby - The Pragmatic Programmer's Guide< /description> < /book> < /section> < /library> < inspect/> #< IO:0x2a06ae8> 

使用ReXML解析XML

REXML 是一個完全用ruby寫的processor ,他有多種api，其中兩個經典的api是通過DOM-like 和SAX-like 來進行區分的。第一種是將整個文件讀進內存，然后存儲為一個分層的形式(也就是一棵樹了).而第二種是"parse as you go",當你的文件很大，并且內存受到限制的時候，比較適合用這種。

看下面的book.xml:

引用

<library shelf="Recent Acquisitions">   <section name="Ruby">     <book isbn="0672328844">     <title>The Ruby Way</title>     <author>Hal Fulton</author>     <description>       Second edition. The book you are now reading.       Ain't recursion grand?     </description>     </book>   </section>   <section name="Space">     <book isbn="0684835509">       <title>The Case for Mars</title>       <author>Robert Zubrin</author>       <description>Pushing toward a second home for the human         race.       </description>     </book>     <book isbn="074325631X">       <title>First Man: The Life of Neil A. Armstrong</title>       <author>James R. Hansen</author>       <description>Definitive biography of the first man on         the moon.       </description>     </book>   </section> </library>

1 Tree Parsing(也就是DOM-like)

我們需要require rexml/document 庫，并且include REXML :

require 'rexml/document' include REXML  input = File.new("books.xml") doc = Document.new(input)  root = doc.root puts root.attributes["shelf"]   # Recent Acquisitions  doc.elements.each("library/section") { |e| puts e.attributes["name"] } # Output: #  Ruby #  Space  doc.elements.each("*/section/book") { |e| puts e.attributes["isbn"] } # Output: #  0672328844 #  0321445619 #  0684835509 #  074325631X  sec2 = root.elements[2] author = sec2.elements[1].elements["author"].text    # Robert Zubrin