2.9 KiB
created_at | title | url | author | points | story_text | comment_text | num_comments | story_id | story_title | story_url | parent_id | created_at_i | _tags | objectID | year | |||
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2013-11-15T10:54:50.000Z | We have an employee whose last name is Null (2010) | http://stackoverflow.com/questions/4456438/how-can-i-pass-the-string-null-through-wsdl-soap-from-actionscript-3-to-a-co?rq=1 | gojko | 67 | 35 | 1384512890 |
|
6738743 | 2010 |
Tracking it down
At first I thought this was a coercion bug where null
was getting
coerced to "null"
and a test of "null" == null
was passing. It's
not. I was close, but so very, very wrong. Sorry about that!
I've since done lots of fiddling on
wonderfl.net and tracing through the
code in mx.rpc.xml.*
. At line 1795 of XMLEncoder
(in the 3.5
source), in setValue
, all of the XMLEncoding boils down to
currentChild.appendChild(xmlSpecialCharsFilter(Object(value)));
which is essentially the same as:
currentChild.appendChild("null");
This code, according to my original fiddle, returns an empty XML element. But why?
Cause
According to commenter Justin Mclean on bug report FLEX-33664, the following is the culprit (see last two tests in my fiddle which verify this):
var thisIsNotNull:XML = <root>null</root>;
if(thisIsNotNull == null){
// always branches here, as (thisIsNotNull == null) strangely returns true
// despite the fact that thisIsNotNull is a valid instance of type XML
}
When currentChild.appendChild
is passed the string "null"
, it first
converts it to a root XML element with text null
, and then tests that
element against the null literal. This is a weak equality test, so
either the XML containing null is coerced to the null type, or the null
type is coerced to a root xml element containing the string "null", and
the test passes where it arguably should fail. One fix might be to
always use strict
equality
tests when checking XML (or anything, really) for "nullness."
Solution
The only reasonable workaround I can think of, short of fixing this bug in every damn version of ActionScript, is to test fields for "null" and escape them as CDATA values.
The only reasonable workaround I can think of, short of fixing this bug in every damn version of ActionScript, is to test fields for "null" and
CDATA values are the most appropriate way to mutate an entire text value that would otherwise cause encoding/decoding problems. Hex encoding, for instance, is meant for individual characters. CDATA values are preferred when you're escaping the entire text of an element. The biggest reason for this is that it maintains human readability.