Hey Pedro,
Welcome to FlexCoders!
I came into E4X with a background in XPath as well and think the
biggest hurdle in learning E4X was understanding the methodology behind
it. XPath is intended as a query language for XML. In contrast I think
of E4X more like an object representation of XML. This means it can
treat results a little differently based on the form of the XML , such
as when you get results with only one subject node but not with
multiple subject nodes. I've found that while I work with XPath from
the top down, I get the best results from E4X when I check it from the
inside out. Here's how the original query works out.
idHTTPService.lastResult.record
.(
[EMAIL PROTECTED]"c001")
The inner most part is @id="c001". The main problem with this is that
it uses the assignment (=) operator and not evaluation (==). This means
that istead of looking for an id attribute value of "c001", it's
actually creating or overrideing the id attribute. So we'll change that
to ==.
idHTTPService.lastResult.record
.(
[EMAIL PROTECTED]"c001")
The next part to evaluate is [EMAIL PROTECTED]"c001". The problem here is
that while @id=="c001" is meant as a filter, it's not in parenthesis.
So we'll change that to subject.(@id=="c001") .
The rest works already, so here's the end result.
idHTTPService.lastResult.record
.(
subject.(@id=="c001"))
It takes a little getting used to, but I've
found that E4X can normally handle what I need it to do.
Ben Stucki
--------------------------------------
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----------------------------------------
From: "Pedro Pastor" <[EMAIL PROTECTED]>
Sent: Friday, February 09, 2007 6:26 PM
To: [email protected]
Subject: [flexcoders] New to the group
Hello to all of you.
I have just entered this
group. I am quite new to those technologies (Flex 2 and ActionScript
3).
After reading some
documentation I'm doing some practising and I have some questions to this
community.
1)
E4X query language:
I'm used to work with XPath for dealing with
XML structures. I've tried to
do some (not very complicated) queries using E4X BUT it seems like E4X doesn't
work the same way (and it is far from fulfilling the XML queries needs). For
example, given the following XML date:
<ROOT>
<record>
<data>..... </data>
<subject id="c001">AAAAAAAA</name>
<subject id="c002">BBBBBBBBBB</name>
<subject id="c003">CCCCCCC</name>
</record>
<record>
<data>..... </data>
<subject id="c001">AAAAAAAA</name>
<subject id="c005">HHHHHHHHH</name>
</record>
And
so on...
</ROOT>
Using an <mx:HTTPService id="idHTTPService"
.. resultFormat="e4x">
And asking for:
idHTTPService.lastResult.record
.(
[EMAIL PROTECTED]"c001")
this
query only provides the record elements that
have ONLY ONE
<subject> child AND has an "@id == c001". I mean, the <record> tags with more
than one
<subject> children always fail.
-
Is this the correct behaviour?
-
How can I perform such type of
query?
Thank
you very much in advance.
Pedro
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