Fetch Grouped Data from Core Data

I have data in a table of messages. These messages are some sort of chat messages. Now I want to fetch the data in form of conversations like this...

Let's suppose we have a,b,c,d,e,f and m users. m is for myself. Now there are messages having senders from a,b,c,d,e,f and m and same is for receiver. All of the messages has m as sender or receiver and one object from other users. Now I want the data to be grouped as..

Groupe A

All messages having messages sent to a or received from a

Groupe B

All messages having messages sent to b or received from b

Groupe C

All messages having messages sent to c or received from c

and so on....

Can any one suggest how I may do that. I've looked into some questions but couldn't find the answer. Any one there to help would be appreciable.

Answers


Using a Fetched Results Controller, you have to consider that some messages will be included more than once.

1) Fetch User entity, sort by name

2) Number of sections: fetchedObjects.count

3) Number of rows in section:

NSSet *allMessages = [user.receivedMessages setByAddingObjectsFromSet:user.sentMessages];
return allMessages.count;

4) Populate the cell:

NSSet *allMessages = [user.receivedMessages setByAddingObjectsFromSet:user.sentMessages];
NSArray *sorted = [allMessages sortedArrayUsingDescriptors:@[[NSSortDescriptor 
            sortDescriptorWithKey:@"message.topic" ascending:YES]]];
Message *m = sorted[indexPath.row];

This can be simplified by adding a transient property to Userthat returns the sorted allMessages. Please not that doing this directly in the datasource methods is not very efficient, I just put it here to illustrate the point.


You can use NSFetchedresultscontroller if is in viewController result. This Object contains a section and row in the result data


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