CODEWITHSUNDEEP
ioscocoa-touchcore-datansfetchrequest
cherbear
cherbear

Reputation: 253

Nested core data fetch

I have a core data DB with multiple entities. There is a parent entity called "Person" which has many "Friends", "Friends" have many "Activities", and "Activities" have "Types" ("Types has a to-many relationship to "Activities"). What I'm trying to achieve is filtering all the "Person" entities by "Types". A user would be tapping on a "Type" and then I would refresh my table and filter the "Person" entities that are displayed by the "Types" that are associated with them.

Currently I'm thinking I have to use a compound predicate but I'm completely sure how to go about it. So far all I've done is printed out the values I've wanted by looping through my fetchedObjects like so: 

NSArray *persons = self.fetchedResultsController.fetchedObjects;


    for (JIPerson *person in persons) {
        JIFriend *friend = person.friends.anyObject;
        JIActivity *activity = friend.activities.anyObject;
        JIType *type = activity.type;
        NSLog(@"%@", type.name);

    }

This prints out the values correctly, but I need to filter my table using these values. How can I achieve that?

Upvotes: 0

Views: 628

Answers (2)

cherbear
cherbear

Reputation: 253

Seems like I got it. Using NSPredicate you can traverse a deep relationship like this using dot notation. My implementation went as follows: 

- (void)filterPersonByType:(NSString *)typeName {

    NSPredicate *typePredicate = [NSPredicate predicateWithFormat:@"ANY friends.activities.type.name CONTAINS[cd]%@", typeName];
}

Upvotes: 2

Rob
Rob

Reputation: 11723

Yes, you can use dot notation with NSPredicate. You might want to have the type be an actual type, though, that would be cleaner than just doing string comparisons.

Upvotes: 0

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