How to get at a relationship items properties in Core Data?

Question

Say you have a Core Data object called Workshop. It has a to-many relationship to a Student object.

How would I create an NSArray of the students within the Workshop?

Answer 1

You usually have no need to create an array of a to-many relationship because they automatically come in a NSSet anyway. This gives better flexibility than an array.

However, if you need students sorted in a particular order you can use a sort descriptor to return a sorted array. Suppose you already have the WorkShop instances and you wanted an array of students sorted by last name in descending order, you would use this:

WorkShop *aWorkShop=//... fetch the appropiate WorkShop instances
NSSortDescriptor *sort=[NSSortDescriptor sortDescriptorWithKey:@"lastName" ascending:NO];
NSArray *sortedStudents=[aWorkShop.students sortedArrayUsingDescriptors:[NSArray arrayWithObject:sort]];