How can my code get notified when the user pastes or drags an image into NSImageView?

Question

I have an instance of NSImageView. I have told InterfaceBuilder to allow the user to paste or drag an image into this view. This works. However, I don't see a way in the NSImageView or related documentation to get notified when this actually happens. I was expecting a delegate or some such, but I have been unable to find it. Any ideas?

Answer 1

This is what Cocoa Bindings does best.

Instead of talking to the view, simply have a property whose value is an image, and bind the image view's image binding to it; then, when you want to change the image in the image view yourself, all you have to do is set the value of the property, and the image view will notice the change.

The user pasting or dragging into the image view is essentially the same thing, partly in reverse: The paste or drop will change the value of the image view, which will then set the value of your property, which will cause anything else bound to it to notice the change and pick up the new value as before.

Aside from ripping out your existing send-explicit-messages-to-views code, this will require almost no code work: The only code you need is for your property. You'll hook up the Binding in IB.

See the Key-Value Coding Programming Guide and the Cocoa Bindings Programming Topics .

Answer 2

As for me the better way to override function

-(void)paste:(id)sender

But only if you have it in NSView based class which has NSResponder as parent