Question

Back again needing more help with constructing my NSPredicates 🙁

Category
{
   name:string
   subs<-->>SubCategory
}

SubCategory
{
   name:string
   numbervalue:NSNumber
}

I would like to know how to create a predicate with AND and OR.

For example, I would like to return every Category with name == “category_name” that also has a subcategory with a numbervalue of “valueA” OR “valueB”.

I’ve tried every possible combination of predicate constructors I could come up with but I just cant get it to work.

This is my best attempt so far.

NSPredicate *predicate=[NSPredicate predicateWithFormat@"(name== %@) AND (ANY subs.numbervalue==%@ OR ANY subs.numbervalue==%@)", @"aname", value1, value2];

Edit 1

Second attempt. The filtering on the ‘numbervalue’ is still not working.

NSNumber valueA=[NSNumber numberWithInt:20];
NSNumber valueA=[NSNumber numberWithInt:90];
NSArray *arr=[NSArray arrayWithObject:valueA,valueB,nil];

predicate=[NSPredicate predicateWithFormat:@"(name==%@)AND(ANY subs.numbervalue IN %@)",@"aname",arr];

Edit 2

I’ve tried filtering just by numberValue and have left the name out alltogether.

1) using this results in the entire set being returned even if only 1 item in the set has the value.

predicate=[NSPredicate predicateWithFormat:@"(ANY subs.numbervalue IN %@)",arr];

2) Using this results in the same problem, every item in the set being returned even if only 1 of them matches.

predicate=[NSPredicate predicateWithFormat:@"((SUBQUERY(subs, $x, $x.numbervalue == %@ or $x.numbervalue == %@).@count > 0)", value1, value2];

Also using the simplest version results in the same problem…. I didnt notice this earlier.

NSPredicate *predicate=[NSPredicate predicateWithFormat@"(ANY subs.numbervalue==%@ ,valueA];

So I think I have my problem narrowed down.

Category is an Entity.
SubCategory is an Entity.

Category has a one to many relationship with SubCategory and is represented as an NSSet of SubCategory.

Each SubCategory has an attribute named numbervalue.

Edit 3

To test I have 2 Categorys.
Both Categories have 10 subs, each with a numbervalue of 1 -10;

Using this code both categories are returned along with all 10 subs for each.

Expected result is both categories returned , each with just 2 subs.

I’ve traced out all my objects and the data is correct. The problem is I cant return a category that has filtered subs.

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSManagedObjectContext *context=[[DataSource sharedDataSource]managedObjectContext];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Category" inManagedObjectContext:context];
[fetchRequest setEntity:entity];

[fetchRequest setFetchBatchSize:20];

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES];
NSArray *sortDescriptors = [NSArray arrayWithObjects:sortDescriptor, nil];

NSPredicate *predicate;
NSNumber *a=[NSNumber numberWithFloat:1];
NSNumber *b=[NSNumber numberWithFloat:2];
predicate=[NSPredicate predicateWithFormat:@"(SUBQUERY(subs,$x,$x.numbervalue==%@ or $x.numbervalue==%@).@count> 0)",a,b];

[fetchRequest setPredicate:predicate];
[fetchRequest setSortDescriptors:sortDescriptors];

NSError *error = nil;
[NSFetchedResultsContoller deleteCacheWithName:nil];

NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:context sectionNameKeyPath:@"name" cacheName:@"Master"];
aFetchedResultsController.delegate = self;

self.fetchedResultsController = aFetchedResultsController;

if (![self.fetchedResultsController performFetch:&error]) {

   NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
   abort();
}

Answer 1

I’ll do the following using a SUBQUERY.

[NSPredicate predicateWithFormat@"(name == %@) AND (SUBQUERY(subs, $x, $x.numbervalue == %@ or $x.numbervalue == %@).@count > 0)", @"aname", value1, value2];

Try it and let me know.

Another solution could be to grab the whole collection subs and then filter the retrieved set with a predicate to check if elements match for value1 or value2.

Hope it helps.

Edit

If you follow Eimantas suggestion make to sure to create the right array:

NSNumber valueA = [NSNumber numberWithInt:20];
NSNumber valueB = [NSNumber numberWithInt:90];
NSArray *arr = [NSArray arrayWithObjects:valueA, valueB, nil];