My Core Data model has a Note entity with a to-many relationship to a Link entity, accessed through a links property on Note.
I'm trying to fetch the count of the links property for each note in Core Data. To do so, I followed the example at the link below, but I'm getting an unexpected result.
Chained expressions to perform calculations in Core Data
Here's how I'm configuring the fetch request and related expression descriptions:
// Create the expression description that should return the link count for each note.
NSExpression *linksExpression = [NSExpression expressionForKeyPath:@"links"];
NSExpression *countExpression = [NSExpression expressionForFunction:@"count:" arguments:@[linksExpression]];
NSExpressionDescription *linkCountExpressionDescription = [[NSExpressionDescription alloc] init];
linkCountExpressionDescription.name = @"linkCount";
linkCountExpressionDescription.expression = countExpression;
linkCountExpressionDescription.expressionResultType = NSInteger32AttributeType;
// Execute a fetch request that should return an array of dictionaries, each with a single "linkCount" key.
NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Note"];
fetchRequest.resultType = NSDictionaryResultType;
fetchRequest.propertiesToFetch = @[linkCountExpressionDescription];
NSArray *countsArray = [self.managedObjectContext executeFetchRequest:fetchRequest error:nil];
The SQLite store I'm working with contains 1000 notes, so I expect to get an array of 1000 dictionaries, each containing a LinkCount key and the count of its links relationship. Instead, I get a single dictionary that gives me the total count of all links.
What should I do differently to get the link counts for each note?
