Question

I have a core data entity named “Folder”. Each “Folder” has a 1-to-many relationship with the entity “File”, and each file contains the field “filename”.

What is a succinct way of producing an array of all of the filenames for a given folder?
I expected it to be something like:

NSManagedObject* folder = [self getSomeFolder];
NSArray* files = [folder valueForKey:@"[e-mail]"];

… but i’ve been having no luck getting it to go, and Apple’s set operations guide has got me stumped.

Answer 1

Your solution is mostly correct, but you need to use -valueForKeyPath: instead of -valueForKey:. -valueForKey: is optimized for keys that do not contain multiple elements (separated by .).