On Sep 24, 2010, at 12:31 PM, Chuck Hill wrote:
>
> On Sep 24, 2010, at 11:26 AM, Alan Ward wrote:
>
>>
>> On Sep 24, 2010, at 12:11 PM, Mike Schrag wrote:
>>
>>> IIRC, the issue is:
>>>
>>> EOEditingContext ec1 = ERXEC.newEditingContext();
>>> ec1.lock();
>>> Car c1 = Car.fetchAllCars(ec1).objectAtIndex(0);
>>> EOEditingContext ec2 = ERXEC.newEditingContext();
>>> ec2.lock();
>>> Car c2 = c1.localInstanceIn(ec2);
>>> c1.setName("New Car Name 1");
>>> c2.setName("New Car Name 2");
>>> ec1.saveChanges();
>>> ec1.unlock();
>>> ec2.saveChanges();
>>> ec2.unlock();
>>>
>>> you don't get an optimistic locking failure in step #6, because the
>>> editingcontext automatically merges changes, and the backing snapshot is
>>> updated.
>>>
>>> Mark would say that you address this by implementing the
>>> editingContextShouldMergeChangesForObject method on EC.Delegate, but IMO,
>>> that really makes your work for it. There is some truth to what Miguel says
>>> ... It does seem odd that within a single instance, you simply don't get OL
>>> failures. You only get them from multiple instances or outside data
>>> editors. To make that delegate behave in the same way, you have to keep
>>> your own snapshot changes in your delegate and check them prior to the EC
>>> committing, essentially implementing OL yourself.
>>>
>>> The proper fix for this is to have the EO keep its original snapshot from
>>> the point when it was brought into the EC, and use THAT for the OL update
>>> clause rather than the shared snapshot cache. The problem with this is that
>>> I think people will constantly get OL failures a LOT more than before for
>>> relatively normal cases. You could probably tweak this behavior to
>>> automerge any object as long as it hasn't been touched in your EC.
>>>
>>> Regardless, Miguel's not totally crazy :)
>>
>> Interesting. I've never really thought about it that way. I've always
>> considered it to be a way to find out if something
>> outside of my app instance changed the data underneath me. If you think
>> about it like that then it works perfectly.
>> Inside my app instance I like to think that I know what's going on and don't
>> need any help from Optimistic Locking
>> but maybe I'm crazy.
>
> My vote is that you are crazy. :-) This becomes an issue in apps where
> users concurrently edit the same object. Out of the box, it is last in wins
> and the second user to save gets no warning that what they are actually
> editing is not what they were looking at.
Right, but there are various ways around that.
Alan
>
> Chuck
>
>
>
>>> On Sep 24, 2010, at 1:33 PM, Alan Ward wrote:
>>>
>>>>
>>>> Maybe I shouldn't ask.... but it's killing me not to. What exactly
>>>> doesn't work about it?
>>>>
>>>> Alan
>>>>
>>>> On Sep 24, 2010, at 10:45 AM, Mike Schrag wrote:
>>>>
>>>>>> because OL doesn't work anyway ;)
>>>>> uh oh .. here he goes again :)
>>>>>
>>>>> ms
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>>
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> --
> Chuck Hill Senior Consultant / VP Development
>
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