How to load all instances of entity / property?

i have some Data in a TableView (loaded from coreData) and now i want to upload this data to a webserver.

Before i can do that i want to save all data to a *.txt file.

How can i load all instances of an entity / property to an mutable array?

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];

[fetchRequest setFetchBatchSize:20];

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"barCode" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];

Thanks, brush51

Edit 1: Can you give me a little Help (i dont want ALL data, just the property "barCode"), now i have this code:

NSManagedObjectContext *moc = [self managedObjectContext];

NSFetchRequest *req = [[NSFetchRequest alloc] init];
[req setEntity:[NSEntityDescription entityForName:@"Event" inManagedObjectContext:moc]];
[req setIncludesPropertyValues:NO];

NSError *error;
NSArray *codes = [moc executeFetchRequest:req error:&error];
[req release];

    for (NSManagedObject *Event in codes) {
    NSLog(@"there it is : ------------> %@", codes);
    NSLog(@"barcodes ----------------开发者_StackOverflow中文版--> %@", [[managedObject valueForKey:@"barCode"] description]);
}  

How to output ONLY the instances of the property "barCode" ??

thanks for answering, here is my code:

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];

[fetchRequest setFetchBatchSize:20];

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"barCode" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];

I have no predicate... Predicate is for what?

If you do a fetch request on the entity without a predicate, you'll get all the instances.