So committedSnapshot records the last committed state so that as yet unsaved
changes can be compared? My value shouldn't change at all in an update ever so
this might be a good place to check for null -> B happening.
What I have noticed in takeStoredValueForKey is that clearProperties() is
invoked if the EO is invalidated, which does lead to a B -> null -> B
transition where in fact the value doesn't change, so I have to ignore the case
where the property goes to null temporarily if an EO is invalidated. Though I
haven't checked that willUpdate() is impacted by clearProperties() in the same
way.
On 11 Sep 2014, at 22:54, Chuck Hill <ch...@global-village.net> wrote:
> That might not give you what you want. committedSnapshot is set when the
> object is first mutated. If you if the value is changed like:
>
> null -> B -> null
>
> Then this won’t log what is desired.
>
> Chuck
>
>
> On 2014-09-11, 12:28 PM, "Theodore Petrosky" wrote:
>
> I have used the
>
> @Override
> public void willUpdate() {
>
> ) method
>
> then I get the original value and compare it
>
> if (committedSnapshotValueForKey(PROJECT_DESCRIPTION_KEY) !=
> NSKeyValueCoding.NullValue) {
> setOldPD((String)committedSnapshotValueForKey(PROJECT_DESCRIPTION_KEY));
>
> }
>
> and in your case check for == NSKeyValueCoding.NullValue
>
> does that do what you want?
>
> Ted
>
>
> On Sep 11, 2014, at 3:20 PM, John Pollard <j...@pollardweb.com> wrote:
>
>> Ray,
>>
>> Thanks for the thought. I do want to log the stack trace but as I can't
>> predict when this issue might happen and it is rare. I want to narrow down
>> to the close circumstances first, or else I will be logging thousands of
>> these stack traces in normal operation when there isn't a problem. What I
>> need to do is detect when a given attribute is changed from non-null to null
>> (which should never happen), so I need to check what it was before it is
>> being set i.e. just check it was non-null before being set to null.
>>
>> John
>>
>> On 11 Sep 2014, at 18:05, Ray Kiddy <r...@ganymede.org> wrote:
>>
>>> On Thu, 11 Sep 2014 14:55:16 +0100
>>> John Pollard <j...@pollardweb.com> wrote:
>>>
>>>> Hi List,
>>>>
>>>> In some debugging within takeValueForKey() I want to find out if the
>>>> key already has a value set. If I call valueForKey() or
>>>> storedValueForKey() and the value isn't already set I get infinite
>>>> recursion as it triggers a fault and tries to load with
>>>> takeValueForKey() and so on.
>>>>
>>>> I am trying to debug where a value is being set to null, but
>>>> apparently not going via validateXXX() or setXXX() methods, so I want
>>>> to trap the case where the takeValueForKey() is passed null when the
>>>> key value was previously non-null and log a stack trace.
>>>>
>>>> Thanks
>>>> John
>>>
>>> One way to prevent the recursion you are talking about is to actually
>>> look at the stack trace inside the method. Call the static method in
>>> Wonder, ERXUtilities.stackTrace(), and look at what is in it. If you
>>> find the method you are in, you have already been called.
>>>
>>> Without Wonder, you can instantiate a Throwable and get the stack trace
>>> from that.
>>>
>>> Doing this is a smell. You do not want to leave this in your code.
>>>
>>> But since you are putting this in to find something, having this check
>>> there temporarily can be useful.
>>>
>>> - ray
>>>
>>>
>>>
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