Mac OS X Core Data distinct values

Asked Mar 23 '16 at 02:26

Active Mar 23 '16 at 04:09

Viewed 52 times

I'm building a Mac OS X application where I'm storing a number of records in core data (i'm also trying in realm), I have a made up example below:

  Num  | rate | factor |
_______|______|________|
   1   |  3.2 |    4   |
   2   |  5.5 |    7   |
   2   |  2.1 |    2   |
   2   |  3.1 |    2   |
   3   |  4.5 |    5   |
   1   |  2.3 |    4   |

I want to get the first row for each Num field. So the result should be as below:

  Num  | rate | factor |
_______|______|________|
   1   |  3.2 |    4   |
   2   |  5.5 |    7   |
   3   |  4.5 |    5   |

What is the most efficient way to do the above fetch? I have read the following on this:

https://developer.apple.com/library/mac/documentation/Cocoa/Reference/CoreDataFramework/Classes/NSFetchRequest_Class/

The unique attributes of Core Data in iOS and Mac OS

https://realm.io/docs/swift/latest/

A simple use case would be as in Messages (for Mac) where it shows the latest message on the left side and the phone number associated with it. It simply does a group by on the number and gets the latest one. How can I achieve this? I have id field which would be the latest one.

edited May 23 '17 at 11:59

Community

asked Mar 23 '16 at 02:26

KVISH

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Possible duplicate of [CoreData get distinct values of Attribute](http://stackoverflow.com/questions/7000768/coredata-get-distinct-values-of-attribute) – FreeNickname Mar 23 '16 at 04:07
Data wise yes, but not from the question. – KVISH Mar 23 '16 at 04:08
You mean from the point of efficiency? – FreeNickname Mar 23 '16 at 04:09
No. I gave update in terms of Messages for mac os. I want the max row of `id` group by on a certain column. – KVISH Mar 23 '16 at 04:10
Oh, so you want to to group the rows by id, and then get the first row from each group? – FreeNickname Mar 23 '16 at 04:16
I have `id`, `name`, `title`. I want to group by on `name` and get the largest `id` row for the `title`. make sense? – KVISH Mar 23 '16 at 04:16
I think it does. Removing the close vote. – FreeNickname Mar 23 '16 at 04:19

Mac OS X Core Data distinct values

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