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Re: Listening for changes on an EO
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Re: Listening for changes on an EO


  • Subject: Re: Listening for changes on an EO
  • From: Lon Varscsak <email@hidden>
  • Date: Thu, 9 Jul 2009 13:45:42 -0700

I want to know if it's being changed.  I have a controller object that
will need to recalculate some values when a specific attribute changes
in the EO.

-Lon

On Thu, Jul 9, 2009 at 1:42 PM, Mark Morris<email@hidden> wrote:
> Just a clarification, do you want to know when the value changes, even if
> it's not saved to the database?  Or do you just want to know if a change is
> being saved?  That would make a difference.  ;-)
>
> Regards,
> Mark
>
> On Jul 9, 2009, at 3:28 PM, Lon Varscsak wrote:
>
>> Uh, another question. :)  Since I have a custom EO super-super class,
>> I decided to try to implement this in takeStoredValueForKey(..).
>>
>> It works, although I was also trying to post the "old" value, and
>> asking for this current value at this point makes EOF not so
>> happy...but that's not strictly required for my needs.
>>
>> However, it does post notifications even for fetched objects, what
>> would be the best way to only post changes after fetching?
>>
>> Thanks again,
>>
>> Lon
>>
>> On Thu, Jul 9, 2009 at 12:43 PM, Lon Varscsak<email@hidden>
>> wrote:
>>>
>>> Thanks for the tips!
>>>
>>> -Lon
>>>
>>> On Thu, Jul 9, 2009 at 12:34 PM, Chuck Hill<email@hidden>
>>> wrote:
>>>>
>>>> On Jul 9, 2009, at 12:26 PM, Lon Varscsak wrote:
>>>>
>>>>> Thanks.  I figured there was nothing built to do exactly what I
>>>>> needed, but I figured I would ask.
>>>>>
>>>>> Do you know if there is much overhead if I implemented this in my EO
>>>>> superclass even if there were no observers?
>>>>
>>>> EOF makes heavy use of notification.  I would not expect there to be
>>>> much
>>>> overhead.  You will probably want to qualify the notification with the
>>>> EC
>>>> (depending on what it is you are trying to do) to limit the number of
>>>> observers.  And then keep the method receiving the notification fast.
>>>>  The
>>>> notifications are synchronous, so you don't want anything slow in this
>>>> method.
>>>>
>>>>
>>>> Chuck
>>>>
>>>>
>>>>
>>>>>
>>>>> -Lon
>>>>>
>>>>> On Thu, Jul 9, 2009 at 11:50 AM, Simon McLean<email@hidden>
>>>>> wrote:
>>>>>>
>>>>>> also, if you are using wonder, check out
>>>>>> hasKeyChangedFromCommittedSnapshot in ERXGenericRecord. maybe listen
>>>>>> for the notification mentioned by chuck, then use
>>>>>> hasKeyChangedFromCommittedSnapshot to check the particular key you are
>>>>>> looking at.
>>>>>>
>>>>>> simon
>>>>>>
>>>>>> 2009/7/9 Chuck Hill <email@hidden>:
>>>>>>>
>>>>>>> On Jul 9, 2009, at 10:24 AM, Lon Varscsak wrote:
>>>>>>>
>>>>>>>> Is there a way for a controller object to listen for changes to an
>>>>>>>> EO
>>>>>>>> (and a specific key)?
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>> Lon
>>>>>>>
>>>>>>> EOEditingContext has ObjectsChangedInEditingContextNotification, but
>>>>>>> it
>>>>>>> is
>>>>>>> on an object by object basis, not a key by key one.
>>>>>>>
>>>>>>> You could implement this in your EO super class.
>>>>>>>
>>>>>>>
>>>>>>> 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
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
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>>>>>>>
>>>>>>
>>>>>
>>>>
>>>> --
>>>> 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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  • Follow-Ups:
    • Re: Listening for changes on an EO
      • From: Chuck Hill <email@hidden>
    • Re: Listening for changes on an EO
      • From: Lon Varscsak <email@hidden>
References: 
 >Listening for changes on an EO (From: Lon Varscsak <email@hidden>)
 >Re: Listening for changes on an EO (From: Chuck Hill <email@hidden>)
 >Re: Listening for changes on an EO (From: Simon McLean <email@hidden>)
 >Re: Listening for changes on an EO (From: Lon Varscsak <email@hidden>)
 >Re: Listening for changes on an EO (From: Chuck Hill <email@hidden>)
 >Re: Listening for changes on an EO (From: Lon Varscsak <email@hidden>)
 >Re: Listening for changes on an EO (From: Lon Varscsak <email@hidden>)
 >Re: Listening for changes on an EO (From: Mark Morris <email@hidden>)

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