Count of tracks in playlists in a playlist folder

count.m

#import <Foundation/Foundation.h>

@interface PlaylistFolder : NSObject
@property (retain) NSArray *playlists;
-(id)trackCount;

@end
@interface Playlist : NSObject
@property (retain) NSArray *tracks;
@end
@interface Track : NSObject
@end



int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
	
	PlaylistFolder *folder = [PlaylistFolder new];
	Playlist *pl1 = [Playlist new], *pl2 = [Playlist new], *pl3 = [Playlist new];
	
	pl1.tracks = [NSArray arrayWithObjects:[Track new], nil];
	pl2.tracks = [NSArray arrayWithObjects:[Track new], [Track new], nil];
	pl3.tracks = [NSArray arrayWithObjects:[Track new], [Track new], [Track new], [Track new], nil];
	folder.playlists = [NSArray arrayWithObjects:pl1, pl2, pl3, nil];
	
	NSLog(@"Folder %@", [folder trackCount]);
	
    [pool drain];
    return 0;
}


@implementation Playlist
@synthesize tracks;
@end
@implementation Track
@end
@implementation PlaylistFolder
@synthesize playlists;
-(id)trackCount;
{
	/////// This is the part I can't figure out
	return [self valueForKeyPath:@"[email protected].@count"];
}
@end

It's [email protected].@count.

AFAIK, @unionOfArrays will evaluate the entire remaining key-path, then union. So the original code tried to union three counts, rather than count a union. (Does that make sense?)

The new code counts each array in playlists.tracks and sums the array of counts.

(This is me randomly reading other programmers' Twitter feeds...)

@sum! Of course! That's what I get for coding when I'm tired. Thanks!