Well, I'm still using -[NSView viewWillMoveToWindow:] to remove my observers
and unbind my bindings, with no problems. But I'm still scared that someday it
might not be invoked when a window is closed. So I filed a bug on the
documentation.
Problem ID: 8172493
Title: -[NSView viewWillMoveToWindow:] always invoked when closed?
Summary:
Documentation of -[NSView viewWillMoveToWindow:] does not clearly state that it
is always invoked when a window is closed.
Steps to Reproduce:
In writing a Cocoa app, one needs a method which is reliably called upon in
which to do various cleanups, such as removing the receiver as an observer or
unbinding.
Expected Results:
The desired method should be well-known and documented.
Actual Results:
One needs to hunt around. The -dealloc or -finalize method comes to mind, but
in the Garbage Collection Programming Guide, "... it is best not to attempt any
work in a finalizer. ... Your design goal should therefore be to not have a
finalizer at all. If you must use a finalizer, you should keep it as short as
possible, and reference as few other objects as possible in its
implementation."
So, other methods should be found. For NSView subclasses, developers have been
using -viewWillMoveToWindow:, like this:
- (void)viewWillMoveToWindow:(NSWindow*)window {
if (window && !m_isObserving) {
[self beginObservingStuff] ;
}
else if (!window && m_isObserving) {
[self endObservingStuff] ;
}
[super viewWillMoveToWindow:window] ;
}
However the documentation for -viewWillMoveToWindow: states only that it
"informs the receiver that it’s being added to the view hierarchy of the
specified window object (which may be nil)."
This implies but does not guarantee that -viewWillMoveToWindow: will be
received when a window will be *closed*. I've never seen it not do this, but
such a statement would be a wonderful addition to the Cocoa documentation.
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