Question

I’ve been looking around and it looks like VDKQueue is a more modern version of UKKQueue, but I’m having trouble implementing it (I’m not great at Cocoa yet).
I have this so far but I’m at a bit of a loss on what else I need (or if this is even right):

VDKQueue *kqueue = [[VDKQueue alloc] init];
[kqueue addPath:path notifyingAbout:VDKQueueNotifyAboutWrite];
[kqueue setDelegate:self];

This answer seems to nicely outline how to set it up, I just don’t really understand it.
Now that I have VDKQueue initialized, how to I set what happens when the file is modified?

Cocoa Monitor a file for modifications

From the other answer:

Implementation was pretty straightforward:

• let your controller be the VDKQueueDelegate; (I added <VDKQueueDelegate> to my AppDelegate.h)
• declare a VDKQueue* ivar / property; (Is this VDKQueue *kqueue = [[VDKQueue alloc] init];?)
• setup delegate method VDKQueue:receivedNotification:forPath:; (How do I do this?)
• init the queue and set its delegate to the controller itself; (is this this [kqueue setDelegate:self];?)
• add resources to watch with addPath:notifyingAbout:. (Added this line [kqueue addPath:path notifyingAbout:VDKQueueNotifyAboutWrite];)

Then just do your business in the delegate method.

Possibly the delegate method from the code?

//
//  Or, instead of subscribing to notifications, you can specify a delegate and implement this method to respond to kQueue events.
//  Note the required statement! For speed, this class does not check to make sure the delegate implements this method. (When I say "required" I mean it!)
//
@class VDKQueue;
@protocol VDKQueueDelegate <NSObject>
@required

-(void) VDKQueue:(VDKQueue *)queue receivedNotification:(NSString*)noteName forPath:(NSString*)fpath;

@end

Answer 1

There are a couple of ways, both of them documented in the VDKQueue header file.

Method A: Notifications

Add an observer on the NSWorkspace’s notification center for the various VDKQueue notifications, listed in that header file. The notification center will call your block (or send a message to your own observer object, if you use that older but still perfectly valid method) when the VDKQueue sends a notification you’re observing for.

Method B: Delegate

You’re already setting yourself as the delegate, which is one of the steps.

Step 1 is to declare that you conform to the VDKQueueDelegate protocol. If you’re not already doing this, you should be getting a warning about it, since setDelegate: requires an object that conforms to the protocol.

Step 2 is to fulfill that promise by actually implementing all of the required methods of the protocol. There’s currently only one.

Step 3 is to set yourself as the delegate.

In your implementation of VDKQueue:receivedNotification:forPath:, which is the method you implemented in step 2, you do whatever you want to do to react to what just happened to the file.