Question

I have an application where I have one custom view which is derived from NSView.
Within this view, there are several custom subviews, which are also derived from NSView.

I want to implement a drag and drop behavior which allows URLs to be dropped onto the views. Everything is already working for the main view.

So, actually I would have to implement dragging behavior handlers on the child-views and the parent-view class.
The thing is, that I don’t want to copy the complete handling code to all the child-views to make them also accept drag events. So I thought that it would be the best way to just let them forward all drag events to the parent view.

Is this possible somehow?? Not sure if I can somehow set this up with the responder-chain maybe?

Any tips are highly appreciated!!
Thanks in advance.

Answer 1

I faced a similar issue where I wanted anything dropped in a view, or any of it’s subviews to be processed by the view, but the calls never got there.

After some research I found this answer to be the most helpful: https://stackoverflow.com/a/7389711/327471

Essentially if a view is not registered to receive any drag events it should pass that information up to it’s parent view automatically. So in my case I ended up with something like this:

NSArray *subviews = [self.view subviews];
for (NSView *aSubview in subviews) {
    [aSubview unregisterDraggedTypes];
}

Of course you can be more precise than that, and make sure to only check subclasses of a certain type or whatever parameters you want. But ultimately the key was unregistering the problem subview from it’s dragged types.

I hope this helps.