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XML Reference Guide

📄 Contents

  1. XML Reference Guide
  2. Overview
  3. What Is XML?
  4. Informit Articles and Sample Chapters
  5. Books and e-Books
  6. Official Documentation
  7. Table of Contents
  8. The Document Object Model
  9. Informit Articles and Sample Chapters
  10. Books and e-Books
  11. Official Documentation
  12. DOM and Java
  13. Informit Articles and Sample Chapters
  14. Books and e-Books
  15. Implementations
  16. DOM and JavaScript
  17. Using a Repeater
  18. Repeaters and XML
  19. Repeater Resources
  20. DOM and .NET
  21. Informit Articles and Sample Chapters
  22. Books and e-Books
  23. Documentation and Downloads
  24. DOM and C++
  25. DOM and C++ Resources
  26. DOM and Perl
  27. DOM and Perl Resources
  28. DOM and PHP
  29. DOM and PHP Resources
  30. DOM Level 3
  31. DOM Level 3 Core
  32. DOM Level 3 Load and Save
  33. DOM Level 3 XPath
  34. DOM Level 3 Validation
  35. Informit Articles and Sample Chapters
  36. Books and e-Books
  37. Documentation and Implementations
  38. The Simple API for XML (SAX)
  39. Informit Articles and Sample Chapters
  40. Books and e-Books
  41. Official Documentation
  42. SAX and Java
  43. Informit Articles and Sample Chapters
  44. Books and e-Books
  45. SAX and .NET
  46. Informit Articles and Sample Chapters
  47. SAX and Perl
  48. SAX and Perl Resources
  49. SAX and PHP
  50. SAX and PHP Resources
  51. Validation
  52. Informit Articles and Sample Chapters
  53. Books and e-Books
  54. Official Documentation
  55. Document Type Definitions (DTDs)
  56. Informit Articles and Sample Chapters
  57. Books and e-Books
  58. Official Documentation
  59. XML Schemas
  60. Informit Articles and Sample Chapters
  61. Books and e-Books
  62. Official Documentation
  63. RELAX NG
  64. Informit Articles and Sample Chapters
  65. Books and e-Books
  66. Official Documentation
  67. Schematron
  68. Official Documentation and Implementations
  69. Validation in Applications
  70. Informit Articles and Sample Chapters
  71. Books and e-Books
  72. XSL Transformations (XSLT)
  73. Informit Articles and Sample Chapters
  74. Books and e-Books
  75. Official Documentation
  76. XSLT in Java
  77. Java in XSLT Resources
  78. XSLT and RSS in .NET
  79. XSLT and RSS in .NET Resources
  80. XSL-FO
  81. Informit Articles and Sample Chapters
  82. Books and e-Books
  83. Official Documentation
  84. XPath
  85. Informit Articles and Sample Chapters
  86. Books and e-Books
  87. Official Documentation
  88. XML Base
  89. Informit Articles and Sample Chapters
  90. Official Documentation
  91. XHTML
  92. Informit Articles and Sample Chapters
  93. Books and e-Books
  94. Official Documentation
  95. XHTML 2.0
  96. Documentation
  97. Cascading Style Sheets
  98. Informit Articles and Sample Chapters
  99. Books and e-Books
  100. Official Documentation
  101. XUL
  102. XUL References
  103. XML Events
  104. XML Events Resources
  105. XML Data Binding
  106. Informit Articles and Sample Chapters
  107. Books and e-Books
  108. Specifications
  109. Implementations
  110. XML and Databases
  111. Informit Articles and Sample Chapters
  112. Books and e-Books
  113. Online Resources
  114. Official Documentation
  115. SQL Server and FOR XML
  116. Informit Articles and Sample Chapters
  117. Books and e-Books
  118. Documentation and Implementations
  119. Service Oriented Architecture
  120. Web Services
  121. Informit Articles and Sample Chapters
  122. Books and e-Books
  123. Official Documentation
  124. Creating a Perl Web Service Client
  125. SOAP::Lite
  126. Amazon Web Services
  127. Creating the Movable Type Plug-in
  128. Perl, Amazon, and Movable Type Resources
  129. Apache Axis2
  130. REST
  131. REST Resources
  132. SOAP
  133. Informit Articles and Sample Chapters
  134. Books and e-Books
  135. Official Documentation
  136. SOAP and Java
  137. Informit Articles and Sample Chapters
  138. Books and e-Books
  139. Official Documentation
  140. WSDL
  141. Informit Articles and Sample Chapters
  142. Books and e-Books
  143. Official Documentation
  144. UDDI
  145. UDDI Resources
  146. XML-RPC
  147. XML-RPC in PHP
  148. Informit Articles and Sample Chapters
  149. Books and e-Books
  150. Official Documentation
  151. Ajax
  152. Asynchronous Javascript
  153. Client-side XSLT
  154. SAJAX and PHP
  155. Ajax Resources
  156. JSON
  157. Ruby on Rails
  158. Creating Objects
  159. Ruby Basics: Arrays and Other Sundry Bits
  160. Ruby Basics: Iterators and Persistence
  161. Starting on the Rails
  162. Rails and Databases
  163. Rails: Ajax and Partials
  164. Rails Resources
  165. Web Services Security
  166. Web Services Security Resources
  167. SAML
  168. Informit Articles and Sample Chapters
  169. Books and e-Books
  170. Specification and Implementation
  171. XML Digital Signatures
  172. XML Digital Signatures Resources
  173. XML Key Management Services
  174. Resources for XML Key Management Services
  175. Internationalization
  176. Resources
  177. Grid Computing
  178. Grid Resources
  179. Web Services Resource Framework
  180. Web Services Resource Framework Resources
  181. WS-Addressing
  182. WS-Addressing Resources
  183. WS-Notifications
  184. New Languages: XML in Use
  185. Informit Articles and Sample Chapters
  186. Books and e-Books
  187. Official Documentation
  188. Google Web Toolkit
  189. GWT Basic Interactivity
  190. Google Sitemaps
  191. Google Sitemaps Resources
  192. Accessibility
  193. Web Accessibility
  194. XML Accessibility
  195. Accessibility Resources
  196. The Semantic Web
  197. Defining a New Ontology
  198. OWL: Web Ontology Language
  199. Semantic Web Resources
  200. Google Base
  201. Microformats
  202. StructuredBlogging
  203. Live Clipboard
  204. WML
  205. XHTML-MP
  206. WML Resources
  207. Google Web Services
  208. Google Web Services API
  209. Google Web Services Resources
  210. The Yahoo! Web Services Interface
  211. Yahoo! Web Services and PHP
  212. Yahoo! Web Services Resources
  213. eBay REST API
  214. WordML
  215. WordML Part 2: Lists
  216. WordML Part 3: Tables
  217. WordML Resources
  218. DocBook
  219. Articles
  220. Books and e-Books
  221. Official Documentation and Implementations
  222. XML Query
  223. Informit Articles and Sample Chapters
  224. Books and e-Books
  225. Official Documentation
  226. XForms
  227. Informit Articles and Sample Chapters
  228. Books and e-Books
  229. Official Documentation
  230. Resource Description Framework (RDF)
  231. Informit Articles and Sample Chapters
  232. Books and e-Books
  233. Official Documentation
  234. Topic Maps
  235. Informit Articles and Sample Chapters
  236. Books and e-Books
  237. Official Documentation, Implementations, and Other Resources
  238. Rich Site Summary (RSS)
  239. Informit Articles and Sample Chapters
  240. Books and e-Books
  241. Official Documentation
  242. Simple Sharing Extensions (SSE)
  243. Atom
  244. Podcasting
  245. Podcasting Resources
  246. Scalable Vector Graphics (SVG)
  247. Informit Articles and Sample Chapters
  248. Books and e-Books
  249. Official Documentation
  250. OPML
  251. OPML Resources
  252. Summary
  253. Projects
  254. JavaScript TimeTracker: JSON and PHP
  255. The Javascript Timetracker
  256. Refactoring to Javascript Objects
  257. Creating the Yahoo! Widget
  258. Web Mashup
  259. Google Maps
  260. Indeed Mashup
  261. Mashup Part 3: Putting It All Together
  262. Additional Resources
  263. Frequently Asked Questions About XML
  264. What's XML, and why should I use it?
  265. What's a well-formed document?
  266. What's the difference between XML and HTML?
  267. What's the difference between HTML and XHTML?
  268. Can I use XML in a browser?
  269. Should I use elements or attributes for my document?
  270. What's a namespace?
  271. Where can I get an XML parser?
  272. What's the difference between a well-formed document and a valid document?
  273. What's a validating parser?
  274. Should I use DOM or SAX for my application?
  275. How can I stop a SAX parser before it has parsed the entire document?
  276. 2005 Predictions
  277. 2006 Predictions
  278. Nick's Book Picks

At this point, we have the basics of the application, so let's take things a step farther. Aside from storing data, the most common thing you'll do with an array is loop through it looking for something. Ruby provides a number of different iterators, which you can use for any structure that involves multiple items, such as an array, list, and so on.

Will start with the each iterator.

The each Iterator

Now it would, of course, be useful for us to be able to iterate through a list of objects. As this is a topic that comes up most frequently with arrays, the let's look to arrays to solve the problem.

Arrays have available to them the each iterator, which literally enables you to iterate through each item in a list. Let's take a look at how it works:

...
puts "The second question is: " 
puts survey.questions[1].questionText
puts "The third answer of the second question is: "
puts survey.questions[1].answers[2].answerText

sequelAnswers.each do |thisAnswer|
   puts thisAnswer.answerText
end

Let's take this apart bit by bit. We start with the array, from which we call the iterator. For each run through the iterator, we want to do something. For that, we are creating a block between the do keyword and the end keyword. Into the block, we are passing the current item for the iterator. We are passing it as thisAnswer, as indicated by the pipe symbols (|).

Each time we run through the block, we can output the answerText attribute of the thisAnswer object. If we execute the script, it looks like this:

Survey is called Retitled Survey
The second question is: 
What is your favorite movie series?
The third answer of the second question is: 
Halloween
Star Wars
Lord of the Rings
Halloween
None of the above

As it happens, we can also nest these blocks:

...
puts "The second question is: " + survey.questions[1].questionText
puts "The third answer of the second question is: " + survey.questions[1].answers[2].answerText

survey.questions.each do |thisQuestion|

   puts thisQuestion.questionText
   thisQuestion.answers.each do |thisAnswer|
      puts "   " + thisAnswer.answerText
   end

end

In this case, we iterate through each of the questions that have been added to the survey, and for each one we output the text, and then iterate through the answers. The result gives us a pretty complete look at the survey:

Survey is called Retitled Survey
The second question is: What is your favorite movie series?
The third answer of the second question is: Halloween
Do you like movie sequels?
   yes
   no
What is your favorite movie series?
   Star Wars
   Lord of the Rings
   Halloween
   None of the above

In fact, this would be useful as the string version for the survey itself:

class Survey
   attr_reader :title, :questions
   attr_writer :title

   def initialize (givenTitle)
      @title = givenTitle
      @questions = Array.new
   end
   
   def to_s
      stringToReturn = "Survey: " + @title
      @questions.each do |thisQuestion|
         stringToReturn = stringToReturn + "\n" + thisQuestion.questionText
         thisQuestion.answers.each do |thisAnswer|
              stringToReturn = stringToReturn + "\n   " + thisAnswer.answerText
         end
      end
      return stringToReturn

   end
   
   def addQuestion(question)
      @questions.push(question)
   end
   
end
...
puts "The second question is: " + survey.questions[1].questionText
puts "The third answer of the second question is: " + survey.questions[1].answers[2].answerText

puts survey

which gives us:

Survey is called Retitled Survey
The second question is: What is your favorite movie series?
The third answer of the second question is: Halloween
Survey: Retitled Survey
Do you like movie sequels?
   yes
   no
What is your favorite movie series?
   Star Wars
   Lord of the Rings
   Halloween
   None of the above

Persisting Objects

Now, I actually had an ulterior motive in creating such a complete string version of the survey, and that's the fact that we are now going to look at saving the object to a file and getting it back out again.

As it happens, saving an object to a file is actually quite straightforward:

...
puts "The second question is: " + survey.questions[1].questionText
puts "The third answer of the second question is: " + survey.questions[1].answers[2].answerText

puts "\n"
puts survey

File.open("savedSurvey", "w+") do |f|
  Marshal.dump(survey, f)
end

newlyLoadedSurvey = nil
File.open("savedSurvey") do |f|
  newlyLoadedSurvey = Marshal.load(f)
end

puts "\nThe new survey is: \n\n"
puts newlyLoadedSurvey

The first step is to get a writable reference to the new file in which we are going to store the object. Notice that as before, the object that is returned by the method, in this case open, is passed to the reference in the pipe symbols, in this case f.

From there, we can use the Marshal class's class method (think static), dump, to save a representation of the object to the file. To get it out again, we create a new object, reopen the file, and load the file's contents into it. Notice that we have not set the type for the newlyLoadedSurvey object; all of the information comes from the persisted data. We can then print the string representation of the object to the command line, as before:

Survey is called Retitled Survey
The second question is: What is your favorite movie series?
The third answer of the second question is: Halloween

Survey: Retitled Survey
Do you like movie sequels?
   yes
   no
What is your favorite movie series?
   Star Wars
   Lord of the Rings
   Halloween
   None of the above

The new survey is:

Survey: Retitled Survey
Do you like movie sequels?
   yes
   no
What is your favorite movie series?
   Star Wars
   Lord of the Rings
   Halloween
   None of the above

Taking Stock

Okay, let's recap. We currently have a Ruby application with three classes, two of which exist as arrays stored and other objects. We looked at basic tasks such as getting information from the command line and outputting it back to the command line, iterating through arrays, and persisting objects in files.

Next, we'll look at putting this Ruby application on Rails.

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