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    <p>The way I resolved this is with Core Data aggregates. I actually end up assigning the ID myself. </p> <p>Essentially, I query Core Data for all of the entity IDs of my entity and then iterate through them. If I find an ID which is higher than the current temporary one, I make the temporary ID higher one higher than the aggregated one. When I'm done, I automatically have an ID which is higher than the highest one in the list. The only flaw I see with this is if there is a missing ID. (I believe that there is a simple fix for this as well.)</p> <pre><code>// // Create a new entity description // NSEntityDescription *entity = [NSEntityDescription entityForName:@"MyEntity" inManagedObjectContext:self.managedObjectContext]; // // Set the fetch request // NSFetchRequest *fetchRequest = [[[NSFetchRequest alloc] init] autorelease]; [fetchRequest setEntity:entity]; // // We need to figure out how many // existing groups there are so that // we can set the proper ID. // // To do so, we use an aggregated request. // [fetchRequest setResultType:NSDictionaryResultType]; [fetchRequest setPropertiesToFetch:[NSArray arrayWithObject:@"entityID"]]; NSError *error = nil; NSArray *existingIDs = [self.managedObjectContext executeFetchRequest:fetchRequest error:&amp;error]; if (error != nil) { // // TODO: Handle error. // NSLog(@"Error: %@", [error localizedDescription]); } NSInteger newID = 0; for (NSDictionary *dict in existingIDs) { NSInteger IDToCompare = [[dict valueForKey:@"entityID"] integerValue]; if (IDToCompare &gt;= newID) { newID = IDToCompare + 1; } } // // Create the actual entity // MyEntity *newEntity = [[MyEntity alloc] initWithEntity:entity insertIntoManagedObjectContext:self.managedObjectContext]; // // Set the ID of the new entity // [newEntity setEntityID:[NSNumber numberWithInteger:newID]]; // // ... More Code ... // </code></pre>
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    1. COYou needn't to fetch all rows - just last using descending sort by id predicate
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    2. COif you uses magical record entity.entityID = @([[Entity findFirstOrderedByAttribute:@"entityID" ascending:NO] entityID].intValue+1);
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