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I'm implementing a -(void)delete: method so I can handle the delete key in my Cocoa app. I want it to do different things depending on what's selected: for text-fields, I want the default behaviour (remove char to the left), but for NSBrowser items, I want it to delete the item.

I thought I would ask the Window for it's first responder, and then see if that first responder is equal to the pointer for my NSBrowser, but it never matched. When I debug it, I find that the firstResponder is pointing to an instance of NSBrowserTableView, but I can't find that in the documentation.

What is it?

And how else could I test to see if my firstResponder is a particular tableView? (I Thought of subclassing NSBrowser but I tend to avoid subclassing, and my second thought was to add a tag, but I like my first method best, if only the firstResponder would point to my NSBrowser instance when one of the items in the browser is selected. )

Thoughts?

Woodster
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2 Answers2

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Actually, @trudyscousin is only partially correct. This class is definitely not a subclass of NSBrowser.

NSBrowserTableView is a private subclass of NSTableView used by NSBrowser to display each column. The table view is used so there is a separate place to draw the branch image (the little arrow drawn next to folders) while leaving the rest of the row to be drawn by either the default or user-defined cell.

If you think about it, it actually makes sense that the table view (rather than the browser) be the first responder, because then the table for the active column gets first crack at responding to keystrokes, and NSBrowser can let NSTableView do what it already knows how to. (For example, jumping to the first row that matches a letter typed by the user.)

Fortunately, NSBrowserTableView has a pointer back to the browser it works for. You can access this via its -(NSBrowser*)browser method. I recommend you don't subclass NSBrowser for this particular case, since you'd have to have a deep knowledge of its private implementation to do anything useful.

Quinn Taylor
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You can't find that in the documentation because it's private. My guess is that, when you instantiate a NSBrowser or a NSTableView, you're actually instantiating a subclass of this private class, which itself is a subclass of NSControl (which is pointed out in the documentation as being the superclass of both NSBrowser and NSTableView). Another example is NSString represented as 'NSCFString,' which I take as an allusion to the fact that CFString and NSString are "toll-free bridged."

Take this with as many grains of salt as you wish, but the way I'd go about gaining insight into the first responder is inserting a NSLog statement in my code and breaking just beyond it, seeing what was printed in the log. You could set the view's tag and display that in the statement. Or you could ask for your first repsponder's class

NSStringFromClass([myFirstResponder class])

and display that.

Hope this helped.

Extra Savoir-Faire
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