Re: Listening for changes on an EO
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 13:46:20 -0700
Sorry I didn't finish the first sentence. I want to know when the
value is being changed regardless of whether it's committed or not.
On Thu, Jul 9, 2009 at 1:45 PM, Lon Varscsak<email@hidden> wrote:
> 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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>
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