gistfile1.m

NSString *fileName = @"foo.json";
NSURL *documentsFolderURL = [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
NSString *filePath = [documentsFolderURL.path stringByAppendingString:fileName];
NSString *jsonString = [[NSString alloc] initWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:NULL];
NSError *jsonError;
NSMutableDictionary *jsonDict = [NSJSONSerialization JSONObjectWithData:[jsonString dataUsingEncoding:NSUTF8StringEncoding] options:NSJSONReadingMutableContainers error:&jsonError];