How to correctly setup a NSPredicate for a to-many relationship when using Core Data?

Question

I have a Core Data model in which a Task entity includes an optional to-many relationship ExcludedDays to the ExcludedDay entity. One of the properties of ExcludedDay is day

Answer 1

Quite curious how to solve this I setup a little project and created the context you are using.

NSDate *today = [NSDate date];
NSMutableArray *objects = [NSMutableArray array];

{
    NSArray *day = [NSArray arrayWithObjects:today, [today dateByAddingTimeInterval:20.0f], nil];
    NSDictionary *excludedDay = [NSDictionary dictionaryWithObject:day forKey:@"day"];
    NSDictionary *object = [NSDictionary dictionaryWithObject:excludedDay forKey:@"excludedDay"];

    [objects addObject:object];
}

{
    NSArray *day = [NSArray arrayWithObjects:[today dateByAddingTimeInterval:20.0f], nil];
    NSDictionary *excludedDay = [NSDictionary dictionaryWithObject:day forKey:@"day"];
    NSDictionary *object = [NSDictionary dictionaryWithObject:excludedDay forKey:@"excludedDay"];

    [objects addObject:object];
}


NSPredicate *predicate = [NSPredicate predicateWithFormat:@"NONE excludedDay.day == %@", today];
NSArray *filtered = [objects filteredArrayUsingPredicate:predicate];

NSLog(@"%@", filtered);

This gives the object when:

1. The day array is empty
2. The day array does not contain the 'today' date

This does not give the object when:

1. The day array contains the 'today'
   • It doesn't matter how many objects in the day array are