NSFetchRequest, Query multiple attributes?

Question

Using NSFetchedResultsController and NSFetchRequest is it possible to setup a query that returns the highest value in each attribute.

For example:

Entity_001 A=F B=27 C=57
Entity_002 A=G B=23 C=98
Entity_003 A=X B=21 C=54
Entity_004 A=K B=11 C=27
Entity_005 A=R B=16 C=15

Result:

Entity_003 A=X B=21 C=54 // Biggest A
Entity_001 A=F B=27 C=57 // Biggest B
Entity_002 A=G B=23 C=98 // Biggest C

Essentially I have one data set and I need to pick out "the smallest", "the fastest" and "the heaviest" I could do it manually without using NSFetchedResultsController, or I guess I could use 3 NSFetchedResultsControllers and try and mesh the results back into a single data source. Any ideas would be very much appreciated ...

J2theC · Accepted Answer · 2012-08-29 13:43:50Z

3

+50

I would do 3 different fetch requests to return the highest value for each particular request, and then merge the object IDs of each particular fetch request result into an array, and perform the NSFetchedResultsController fetch (to have notifications from changes) with a fetch request that looks for the IDs of the objects inside the array. Basically, it's 4 fetches. Three can be done in the background, one for the NSFetchedResultsController instance which will be done in the main thread.

answered Aug 29, 2012 at 13:43

J2theC

4,4621 gold badge14 silver badges14 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

fuzzygoat Over a year ago

Much appreciated Sir, just what I was after.

craig1231 · Accepted Answer · 2012-08-23 20:42:02Z

1

Have you tried looking at KeyValue Coding?

answered Aug 23, 2012 at 20:42

craig1231

3,8944 gold badges33 silver badges34 bronze badges

1 Comment

fuzzygoat Over a year ago

This looks promising, but am I right in thinking this works directly on the managed object context and not via NSFetchedResultsController?

Collectives™ on Stack Overflow

NSFetchRequest, Query multiple attributes?

2 Answers 2

1 Comment

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related