Guessing, concurrent threads, and locking.  Never a good combination.

On Aug 11, 2010, at 2:35 PM, Farrukh Ijaz wrote:

> I am using ERXEC with default settings. I guess it takes care of the locking 
> automatically.
> 
> Sent from my iPad
> 
> On 11-Aug-2010, at 11:58 PM, Chuck Hill <[email protected]> wrote:
> 
>> 
>> On Aug 11, 2010, at 1:41 PM, Farrukh Ijaz wrote:
>> 
>>> 
>>> 
>>> Sent from my iPad
>>> 
>>> On 11-Aug-2010, at 7:35 PM, Chuck Hill <[email protected]> wrote:
>>> 
>>>> 
>>>> On Aug 11, 2010, at 2:11 AM, Farrukh Ijaz wrote:
>>>> 
>>>>> Hi All,
>>>>> 
>>>>> Is it safe to invoke editingContext().saveChange() or 
>>>>> editingContext().revert() in a method that is used through NSSelector and 
>>>>> invoked by the NSNotificationCenter on postNotification()?
>>>> 
>>>> 
>>>> That likely depends on which notification.
>>> 
>>> Okay, here is the real scenario. I have developed a Workflow Engine which 
>>> is capable to run multiple workflows in parallel in their individual 
>>> threads. Each workflow has methods as start(), stop(), suspend(), and 
>>> resume(). The behavior of these methods is understood. Everything remains 
>>> in memory. Now in order to persist their state I have created a 
>>> corresponding entity. There are two columns of the entity, status and 
>>> serializedInstance which change at any stage and that is depending upon 
>>> user actions and workflow code.
>>> 
>>> I have a workflow management dashboard which provides ability to view all 
>>> the workflows defined in the system and to start, stop, resume and suspend. 
>>> When I start the workflow, I call the method start() of the workflow 
>>> entity, which internally triggers the associated workflow's start() method 
>>> and also registers the entity to receive notifications from the workflow 
>>> thread. The workflow thread post notifications such as when it completes 
>>> the job or explicitly stopped, resumed, suspended etc. So upon these 
>>> notifications, the workflow entity's onNotify() method is invoked which in 
>>> turn based on the message, modifies the status column and 
>>> serializedInstance column value and invokes, editingContext().saveChanges() 
>>> inside the onNotify() method.
>> 
>> You will have to make sure that the EC is locked before touching any of the 
>> entity's persistent values or calling saveChanges()
>> 
>>> 
>>> I guess the story is too long but it is working fine so far. I just want to 
>>> confirm that if this does not break anything at any stage or cause a 
>>> deadlock situation?
>>> 
>>>> 
>>>> Chuck
>>>> 
>>>> -- 
>>>> Chuck Hill             Senior Consultant / VP Development
>>>> 
>>>> Practical WebObjects - for developers who want to increase their overall 
>>>> knowledge of WebObjects or who are trying to solve specific problems.    
>>>> http://www.global-village.net/products/practical_webobjects
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>> 
>> -- 
>> Chuck Hill             Senior Consultant / VP Development
>> 
>> Practical WebObjects - for developers who want to increase their overall 
>> knowledge of WebObjects or who are trying to solve specific problems.    
>> http://www.global-village.net/products/practical_webobjects
>> 
>> 
>> 
>> 
>> 
>> 
>> 

-- 
Chuck Hill             Senior Consultant / VP Development

Practical WebObjects - for developers who want to increase their overall 
knowledge of WebObjects or who are trying to solve specific problems.    
http://www.global-village.net/products/practical_webobjects







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