-draggingEnded

[Christiaan Hofman]

On 14 Nov 2007, at 4:52 PM, David Dunham wrote:

>
> On 14 Nov 2007, at 01:44, Christiaan Hofman wrote:
>
>> NSDraggingSource is an informal protocol, which means it may be  
>> implemented in some views (like NSTableView) and in other cases  
>> you may have to implement it yourself. I don't know what  
>> CellEditor is, but it sure does not sound like a subclass of a  
>> view that implements it.
>
>
> CellEditor is my class, and I do implement draggingEnded:. The  
> exception comes when I call super (an NSTextView).
>
> It's even worse -- I changed the code to
>
> - (void) draggingEnded: (id <NSDraggingInfo>) aSender
> 	// ...
> 	if ([super respondsToSelector: @selector(draggingEnded:)])
> 		[super draggingEnded: aSender];
>
> and still get unrecognized selector.
>

That code is totally wrong. It does not check whether the superclass  
implements draggingEnded:, it just uses the superclass's  
implementation of -respondsToSelector: to check whether the object  
itself implements it ('super' does not change the receiver, only the  
method implementation). As this is the same as self's implementation,  
your code is equivalent to:

- (void) draggingEnded: (id <NSDraggingInfo>) aSender
	// ...
	if ([self respondsToSelector: @selector(draggingEnded:)])
		[super draggingEnded: aSender];

and as you're guaranteed to implement to draggingEnded: it is  
equivalent to:

- (void) draggingEnded: (id <NSDraggingInfo>) aSender
	// ...
	if (YES)
		[super draggingEnded: aSender];

So it's no wonder it will fail. You should do this:

	if ([[CellEditor superclass] instancesRespondToSelector:_cmd])
		[super draggingEnded: aSender];

As a general remark on your question, note that the release notes do  
not say *where* draggingEnded: is implemented, only that it is  
implemented *somewhere*. Certainly, it is not implemented everywhere  
(i.e. in NSObject). Maybe it is only *called* at the correct time  
now? I agree they should have indicated what they mean with this  
sentence, because it basically contains no information.

Christiaan


> David Dunham
> Voice/Fax: 206 783 7404             http://www.pensee.com/dunham/
> Imagination is more important than knowledge. -- Albert Einstein
>
>
> David Dunham     A Sharp, LLC
> Voice/Fax: 206 783 7404     http://a-sharp.com
> Efficiency is intelligent laziness.
>
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