Comments on: E4X tip: writing expressions to test attributes that may not exist

By: Danny Kopping

Danny Kopping — Tue, 03 May 2011 23:11:23 +0000

You rock Mr Morearty!

By: Bart vbl

Bart vbl — Mon, 05 Jul 2010 10:32:17 +0000

Thanks for saving me a LOT of time which I'd have spent figuring this out myself ^^

By: Jesse Freeman

Jesse Freeman — Thu, 28 Aug 2008 19:04:00 +0000

Thanks for this post, for the past 30 mins I thought I was going nuts. This did the trick, keep up the good work!

By: Oleg

Oleg — Thu, 17 Jan 2008 11:51:21 +0000

Thanks. This trick saved me time.

By: mike

mike — Thu, 03 Jan 2008 06:12:06 +0000

Rick, use the elements() function, and test that the XMLList returned by the elements() function has a length of 1 or greater. For example, to return a list of nodes of type "child", but only those ones that contain another element called "grandchild":

var myxmlvar:XML = ; var mylist:XMLList = myxmlvar.thing1.(elements("thing2").length() > 0);

To learn more about functions such as attribute() and elements(), see the documentation for class XML ( http://livedocs.adobe.com/flex/201/langref/XML.html ) and class XMLList ( http://livedocs.adobe.com/flex/201/langref/XMLList.html ).

By: Rick T

Rick T — Thu, 03 Jan 2008 02:35:53 +0000

A great suggestion. I hope you don't mind that I mentioned your blog on the Adobe site in response to a query about this topic.

BTW, do you have any suggestions for the best technique for testing for existence of a node?

By: William G

William G — Tue, 16 Oct 2007 08:54:47 +0000

Thanks!!! Your post saved me some hours ! I don't know if it's only me but the Flex doc is sometimes hard to understand...especially the XML/XMLList part...

By: mike

mike — Sun, 28 Jan 2007 07:29:30 +0000

Yes, selectedNode.hasOwnProperty() can be used to tell whether an attribute is present on a node, which is sufficient in some cases; but usually, you want to test for certain values. For example, if you want to select only nodes that have an "x" attribute equal to "y", then using hasOwnProperty, you would have to write

hasOwnProperty("@x") && @x == "y"

whereas if you use the attribute() function, it's cleaner:

attribute("x") == "y"

By: Alex

Alex — Sat, 27 Jan 2007 23:18:15 +0000

if (selectedNode.hasOwnProperty("@link") == true) {

By: Marcus

Marcus — Thu, 02 Nov 2006 07:27:56 +0000

Thanks Mike. Handy tip. And its not really that ugly...