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E4X XML Namespaces

For XML that looks like the following response from Yahoo's weather service:

PLAIN TEXT
XML:
  1. <?xml version='1.0' encoding='UTF-8'?>
  2. http://us.rd.yahoo.com/dailynews/rss/weather/Sunnyvale__CA/*
  3. http://weather.yahoo.com/forecast/94089_f.html         Yahoo! Weather for Sunnyvale, CA
  4. en-us
  5. Tue, 06 Nov 2007 6:56 pm PST
  6. 60
  7.  
  8.  
  9.  
  10.  
  11.  
  12. <img alt="" />
  13.  
  14. 142
  15. 18
  16.  
  17. http://weather.yahoo.com/             http://l.yimg.com/us.yimg.com/i/us/nws/th/main_142b.gif
  18. 37.39
  19. -122.03
  20.  
  21. http://us.rd.yahoo.com/dailynews/rss/weather/Sunnyvale__CA/*http://weather.yahoo.com/forecast/94089_f.html Tue, 06 Nov 2007 6:56 pm PST
  22.  
  23. &lt;![CDATA[
  24. <img src="http://l.yimg.com/us.yimg.com/i/us/we/52/33.gif" alt="" />
  25. <strong>Current Conditions:</strong>
  26. Fair, 55 F
  27.  
  28. <strong>Forecast:</strong>
  29. Tue - Mostly Clear. High: 67 Low: 49
  30. Wed - Partly Cloudy. High: 71 Low: 49
  31.  
  32. <a href="http://us.rd.yahoo.com/dailynews/rss/weather/Sunnyvale__CA/* http://weather.yahoo.com/forecast/94089_f.html">Full Forecast at Yahoo! Weather</a>
  33. (provided by The Weather Channel)
  34. ]]&gt;
  35.  
  36.  
  37.  
  38. 94089_2007_11_06_18_56_PST

When you need to access the nodes with complex node names such as yweather:location think XML namespaces.
In the above example, look for the xmlns declaration in the rss node
- xmlns:yweather='http://xml.weather.yahoo.com/ns/rss/1.0'.
Creating a Namespace object using the declaration will allow us to access the nodes with complex names.
Creating a Namespace object is a pretty simple process:

PLAIN TEXT
Actionscript:
  1. var yweatherNS:Namespace = new Namespace( http://xml.weather.yahoo.com/ns/rss/1.0 );

Now we can access the node with the following code:

PLAIN TEXT
Actionscript:
  1. yahooWeaterXML.channel.yweatherNS::location
  2.  
  3. trace( yahooWeaterXML.channel.yweatherNS::location.@city ); // outputs 'Sunnyvale'
  4. trace( yahooWeaterXML.channel.yweatherNS::location.@region); // outputs 'CA'
  5. trace( yahooWeaterXML.channel.yweatherNS::location.@country ); // outputs 'US'

With the preceding example we need to know the namespace url ahead of time. E4X gives us the namespaceDeclarations() method that will return an array that contains the namespace declarations associated with the XML document

Using the namespaceDeclarations() method from the XML object:

PLAIN TEXT
Actionscript:
  1. var namespaces:Array = myXML.namespaceDeclarations();

Now we have an array of namespace declarations that we can use to dynamically declare Namespace objects and access our complex node names:

PLAIN TEXT
Actionscript:
  1. var yweatherNS:Namespace
  2. var geoNS:Namespace
  3. var nsLen:uint = nameSpaces.length;
  4. for(var i:uint = 0; i &lt;nsLen; i++)
  5. {
  6. var newNamespace:Namespace = new Namespace( nameSpaces[i] );
  7. if( String( nameSpaces[i].prefix ).toLowerCase() == "yweather" )
  8. {
  9. yweatherNS = newNamespace;
  10. }
  11. else
  12. {
  13. geoNS = newNamespace;
  14. }
  15. }

So we can access the geo and yweather nodes without any problems now.

Posted in news. Tagged with , , , , , .

By John
November 6, 2007