Core Data: NSPredicate for many-to-many relationship. (“to-many key not allowed here”)

You’re trying to compare a collection (categories.name) to a scalar value (category.name). You need to either use a collection comparator (CONTAINS), or use a predicate modifier (ANY/ALL/SOME, etc).

Try using:

[NSPredicate predicateWithFormat:@"ANY categories.name =[cd] %@", category.name];

Or:

[NSPredicate predicateWithFormat:@"categories.name CONTAINS[cd] %@", category.name];