Re: -setTarget: and -setAction: of NSImageView

[Kazunobu Kuriyama]

Alexander Malmberg wrote:

> Kazunobu Kuriyama wrote:
> [snip]
>
> > > > Therefore, contrary to my expectation (as well as everybody's, I hope),
> > > > NSImageView doesn't accept both of two methods.
> > > The current behavior is consistent with the documentation, and since an
> > > NSImageView/NSImageCell doesn't actually send any actions to any
> > > targets, it's fairly sensible to have it raise an exception for these
> > > methods.
> > Consistent?  But NSImageView is a subclass of NSControl, why can't
> > I expect NSImageView accepts the methods?
>
> How do you define "accept"? The NSImageView does respond to these
> messages, and sends them on to NSImageCell, which also responds and
> raises an exception, as documented. If you used a different cell (a
> custom cell, or eg. an NSActionCell), you'd see different behavior.
By "accept", I mean whatever one can expects from the target/action
paradigm.  The behavior you mention is GNUstep's one due to the
current implementation.  I understand this very clearly.  So
I send the email to bug-gnustep because I think it is a bug.

> > I think my expectation
> > is quite natural.  I also read AppKit.pdf, but I can't find
> > there that NSImageView is allowed to reject the methods.
>
> The documentation makes it clear that NSControl merely sends -setTarget:
> and -setAction: on to its cell, and it also makes it clear that
> NSImageCell raises an exception when you send those messages to it.
> Anyway, I'll ask again:
Then, why is NSViewImage a subclass of NSControl?  I think
there is a gap in your argument.  To be sure, NSControl sends
-setTarget: and -setAction: on its cell.  True, NSImageCell raises
an exception when it gets -setTarget: or -setAction:.  But you
fail to fill the gap between the two statements.

> > > What behavior did you expect?
>
> Ie. when you call [anImageView setTarget: foo];, what do you except the
> image view/cell to do? Silently ignore the call, or somehow use the
> target? If so, how? When does it send an action?
In a class, NSImageView is used as an outlet.  The class is a bare-bones
version of NSDocument.  By setting
 [anImageView setTarget: self];
 [anImageView setAction:  aMethodOfSelf];
the class is designed to reflect the change of the image contained in
an NSImageView (edit or drag-and-drop) to the viewer's size and
a flag indicating that the image is modified.

> [snip]
>
> > > Don't call -setTarget: and -setAction: on an NSImageView? :)
> > Hmm...  I found that problem when I was trying an example of S. Anguish,
> > E.M. Buck and D.A. Yacktman, "Cocoa Programming", SAMS, 2002.  Do you
> > mean they give a wrong usage of NSImageView?  That's beyond my judgement.
>
> Without seeing the example, I can't say what they're trying to do, or
> whether it's correct.
Attached is the sample code taken from the book.
(http://www.cocoaprogramming.net)
You can see the "problematic" usage of NSImageView in MYDocument.m

> Also, why did you reply in private? The mailing list is more appropriate
> since others might be interested in the discussion, or know something
> about issue.
Sorry for that.  I don't know why it happend and didn't do that purposely.
Hope this email goes to the right place.

> - Alexander Malmberg
>
>

ImageViewer2.tar.gz
Description: GNU Zip compressed data