CODEWITHSUNDEEP
iosswiftuitableviewcore-datanspredicate
Andrew
Andrew

Reputation: 7883

Predicates and combined filters in core data?

I'm not using Core Data currently, but I'm about to switch to it from Realm, if I'm sure a certain thing will work, which is vital to the way my application currently works. I have a model with two objects:

Message:
date - NSDate
text - String
images - One-to-many > Image

Image:
imageURL - String
message - Many-to-one > Image

I have a table view which displays both Images and Messages. I need to know what should go at a certain index path, for when UITableView wants to know. So I need to be able to perform a query akin to:

"Give me an ordered list of images and messages, messages sorted by their date and images sorted by their message.date".

How could I do this?

Upvotes: 0

Views: 81

Answers (1)

dopcn
dopcn

Reputation: 4218

As far as I know you can't sort a mixed array with messages and images during coredata fetch request. Here is one possible way:

  1. fetch messages and images separately
  2. merge two arrays into one
  3. sort the only one array - (NSArray *)sortedArrayUsingFunction:(NSInteger (*)(id, id, void *))comparator context:(void *)context

the function

 NSInteger sort(id item1, id item2, void *context) {
        int v1 = [item1 iskindofClass[message class]]?item1.data:item1.message.date;
        int v2 = [item2 iskindofClass[message class]]?item1.data:item1.message.date;
        if (v1 < v2)
            return NSOrderedAscending;
        else if (v1 > v2)
            return NSOrderedDescending;
        else
            return NSOrderedSame;
    }

Upvotes: 1

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