On 28/07/2011 13:53, Wolfgang Laun wrote:
Two points to consider:
(1) If a programmer writes
a.getB().getC() == <something>
and a NPE happens due to a.getB() == null we may distinguish (a) and
(b) - see below.
(a) The setup is so that this is to be expected but the programmer
forgot to take this possibility into account. Then we have:
(a1) The consequence of a.getB() == null should be the same as
a.getB().getC() == null.
(a2) If a.getB() == null, something else needs to be done, e.g.,
a.setB(x). If this is silently covered by the system, the absence of
handling will not be detected so easily.
(b) The assumption is that a.getB() should never be == null in the
first place, but some other error (in data or code) caused this. If
this is silently covered by the system, this error will not be
detected so easily.
(2) If a.getB().getC() == <something> returns false if a.getB() is
null, is this also the desired result if <something> is "null", i.e.,
do you want
a.getB().getC() == null
to be false if a.getB() == null ?
"Null safe navigation" is a nice try and *may* be tolerable, but it
should never be the default.
ok, sounds like we just need to add .? support into our parser then - if
it's not already supported.
Mark
-W
On 28 July 2011 14:06, bolsover <da...@bolsover.com
<mailto:da...@bolsover.com>> wrote:
Thanks for the pointer to the MVEL documents - I can forsee null-safe
operator user.?manager.name <http://manager.name> syntax being
most useful.
As for making the null test the default action - I'm not sure - I
can't say
I have ever actually 'wanted' a nullpointer - but there may be
some special
case.
David
--
View this message in context:
http://drools.46999.n3.nabble.com/Condition-syntax-to-access-Map-tp3204429p3206467.html
Sent from the Drools: User forum mailing list archive at Nabble.com.
_______________________________________________
rules-users mailing list
rules-users@lists.jboss.org <mailto:rules-users@lists.jboss.org>
https://lists.jboss.org/mailman/listinfo/rules-users
_______________________________________________
rules-users mailing list
rules-users@lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
_______________________________________________
rules-users mailing list
rules-users@lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
