Flex Monkey Patches

XML and ampersands do not mix well.
Flex uses mxml which is XML.
This can lead to issues when writing binding expressions in mxml tags for component properties when you are trying to write logical expressions using ‘and’.

Here is a simple sample that demonstrates how to escape the ampersands in the expression and how to create a logical expression that does not even use ‘and’, but achieves the same result.

Browse the source of this example.
Download a zipfile containing the source to this sample.

I recently had an issue from a customer regarding figuring out the correct syntax to get at a few nodes in an XML object that had namespaces using e4x. Now I don’t know about you, but if I don’t use e4x often, I forget things and get rusty. If your e4x-foo is weak, here are a few references that I found useful:

http://www.darronschall.com/weblog/archives/000223.cfm
(In fact Darren has a few e4x entries aside from this one.)

http://www.partlyhuman.com/blog/roger/as3-e4x-rundown

Hope this helps,

-Kyle

E4X is a very powerful and easy way to manipulate xml data in Flex.
Of course something so p[powerful can sometimes be confusing when it produces unexpected results.

If you wanted to retrieve the price of the burger menuitem above, it is easily done with the e4x expression:

Then if you used the same expression, you actually would not get a value returned.
It is not obvious as to why this happens, but of course there is more than one way to skin a cat…
Here is an expression that will work:

Here is a link to a Flex Builder 2.0.1 project (compiled with SDK hotfix1) containing a sample demonstrating the solution described above.