I am working with my Cocoa app to be scriptable by Python and Ruby
using ScriptingBridge as well as by AppleScript. It is all working
well, but I hit a serious issue today when I ran a long script. A
python script that is fine and thoroughly checked will crash if it
runs a long time. It crashes with no message to the Console or to
standard error. It crashes both when I run using tools in my Cocoa app
or if it is run from Terminal app. I got it to work with a script
rewrite, but it raises some serious concerns.
I reduced the problem to these two loop fragments. Note: the question
here is about the Cocoa ScriptingBridge and not about these python
code fragments, hence the reason to post on this Cocoa list. The issue
must be related to how these commands trigger Apple Events through the
Scripting Bridge. In these scripts, recs is an SBElementArray with a
collection of objects from my app. The methods birthSDN() and
birthSDNMax() are properties of my app's Cocoa objects and thus will
trigger an AppleEvent to read them.
Method 1:
for indi in recs:
emin=indi.birthSDN()
emax=indi.birthSDNMax()
if emin!=0 and emin==emax:
(code to save details on indi)
Method 2:
emin=recs.arrayByApplyingSelector_("birthSDN")
emax=recs.arrayByApplyingSelector_("birthSDNMax")
for i in range(len(recs)):
if emin[i]!=0 and emin[i]==emax[i]:
(code to save details on indi)
Method 1 crashes if len(recs) is above about 6000. Method 2 is much
faster and has not crashed yet (but I haven't tried huge files). The
idea for method 2 came from Apple ScriptingBridge documentation that
recommended using [SBElementArray arrayByApplyingSelector:] whenever
possible. Specifically it says:
"As a corollary to the above guideline, avoid enumerating
SBElementArray objects if there are alternatives, which Scripting
Bridge and Cocoa provide..."
and then mentions [SBElementArray arrayByApplyingSelector:] (and some
other tools). To check if "enumerating" was the problem, I modified
method 1 to be
Method 1b:
for i in range(len(recs)):
indi=recs[i]
emin=indi.birthSDN()
emax=indi.birthSDNMax()
if emin!=0 and emin==emax:
(code to save details on indi)
This version lasts longer than Method 1, but still crashes before
long. I counted the total number of Apple Events triggered in these
loops. The crashes occur in the range of 16000 to 20000 events.
My concern is that the ScriptingBridge does not scale to long scripts
and will always crash if too many AppleEvents are triggered. I would
be happy if method 1 was just inefficient and slow (as implied by the
documentation), but it is a serious problem if inefficient (but valid)
scripts are crashing. Furthermore, I am working on numerous other
scripts and method 2 simply cannot be used. Thus, while I try to
"avoid" method 1, it cannot always be avoided?
------------
John Nairn
http://www.geditcom.com
Genealogy Software for the Mac
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