Re: User interface validation doesn't work, right?
Re: User interface validation doesn't work, right?
- Subject: Re: User interface validation doesn't work, right?
- From: Keary Suska <email@hidden>
- Date: Wed, 1 Jul 2009 17:00:26 -0600
On Jul 1, 2009, at 3:24 PM, Bill Cheeseman wrote:
For years, the "Implementing Validation" section of Apple's "User
Interface Validation" document has said the following:
"Before it is displayed, a user interface item checks to see if its
target implements validateUserInterfaceItem:. If it does, then the
enabled status of the item is determined by the return value of the
method. You can therefore conditionally enable or disable an item by
implementing validateUserInterfaceItem: in the target object."
This has never been true. Right?
No, I would say it is usually true, but not always.
My custom window controller implements the action method for a
button, so it is the button's target, and it also implements -
validateUserInterfaceItem:, all according to the User Interface
Validation document. But my -validateUserInterfaceItem: method is
never called.
Implementing the action method isn't sufficient, BTW. The object must
also be the current target (i.e. first responder for nil-targeted
actions, or designated target). Also note that not all user interface
items do this--they must conform to the NSValidatedUserInterfaceItem
(or NSUserInterfaceValidations) protocol, which IIRC NSButton does
not. In fact, I think only menu items and toolbar items do.
If I want it to be called automatically, by analogy to -
validateMenuItem:, I have to override NSWindow's -update method, by
analogy to -[NSMenu update]. In my override of -update, I have to do
for myself what the document claims already happens -- or I have to
observe NSWindow's -NSWindowDidUpdateNotification. Right?
Keary Suska
Esoteritech, Inc.
"Demystifying technology for your home or business"
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