Re: CoreData "in" predicate
Re: CoreData "in" predicate
- Subject: Re: CoreData "in" predicate
- From: Frederick Reimer <email@hidden>
- Date: Sun, 2 May 2010 16:32:15 -0400
Unfortunately, there is nothing for the NSPredicate class to go on to assume what object you are talking about. predicateWithFormat is a class method/selector/function. What object is it supposed to assume you mean if one is not supplied?
Dan Rowley sent me an email saying you may be able to use "self." So, I assume this means:
NSPredicate *pred = [NSPredicate predicateWithFormat: @"%K in %@", self, favoriteMissions];
HTH,
On May 2, 2010, at 9:03 AM, Rick Mann wrote:
> I saw that, I had hoped that by not specifying an attribute, it would mean the object itself, not an attribute on the object.
>
>
> On May 2, 2010, at 05:58:39, Frederick Reimer wrote:
>
>> The manuals for this give the following example:
>>
>> NSPredicate *inPredicate =
>> [NSPredicate predicateWithFormat: @"attribute IN %@", aCollection];
>>
>> It looks like you are missing the attribute... If attribute can vary, you can use a %K and a NSString value representing the attribute name (it is not automatically enclosed in quotes as %@ values are).
>>
>> HTH,
>>
>> Fred
>> On May 2, 2010, at 8:27 AM, Rick Mann wrote:
>>
>>> Hi.
>>>
>>> I have two entities: Mission and Favorite. Favorite has a single relation to Mission. I need to fetch all Mission objects that exist in Favorite. I'm using an NSFetchResultsController.
>>>
>>> I created an array with all the Mission objects found in the Favorite entity. Then I tried to create a predicate like this:
>>>
>>> NSPredicate* pred = [NSPredicate predicateWithFormat: @"in %@", favoriteMissions];
>>>
>>> and use that on a fetch of Mission objects. But it complains that it can't parse that format string.
>>>
>>> Clearly, this approach isn't going to work. I could store the Mission's key in the Favorite table instead, but that's less elegant. Might be the only way to go.
>>>
>>> Any suggestions?
>>>
>>> tia,
>>> Rick
>>>
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>>
>
>
Fred Reimer, CCIE 23812 CISSP 107125
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