Taking advantage of validateUserInterfaceItem

Most of you will already know how convenient it is to use -validateMenuItem: and -validateToolbarItem: in your controller to make sure the toolbar/menu items are accurately enabled. These methods also let you perform some more accurate validation than simply "first responder provides that function"; for example, you can check whether there is anything selected and disable the "clear" menu item for your custom view. One of the annoyances of this approach is that usually toolbar items duplicate items that already exist in the menus, forcing you to write a dummy-validateToolbarItem that just calls through to validateMenuItem. But there's an easier way than that:

If you do not provide -validateMenuItem: or -validateToolbarItem:, AppKit will instead call -validateUserInterfaceItem: for both of them. So, if you have menu items that are also available on the toolbar, this method lets you use the same method to validate them both.

But this often-overlooked method isn't reason enough for a blog entry. What is, is that you can also use this method to validate buttons in your window. Well, not out of the box, but with help from a small method. Most apps have an -updateUI method in some controller that uses dozens of outlets to set up all buttons in your window according to the current state of the model. Let's replace that method with another one and get rid of all those outlets:

-(void)    updateUI
{
    NSWindow*       win = [self window];
    NSView*         cView = [win contentView];
    NSEnumerator*   enny = [[cView subviews] objectEnumerator];
    NSView*         sView = nil;
    
    while( (sView = [enny nextObject]) )
    {
        if( [sView isKindOfClass: [NSButton class]] )
        {
            [(NSButton*)sView setEnabled: [self validateUserInterfaceItem: sView]];
        }
    }
}