more on two-way bindings and one-way bindings

FROM : Matt Neuburg
DATE : Thu Jul 06 22:03:59 2006

Okay, this one is even weirder.

In IB, you've got an NSObjectController and MyObject. Bind
NSObjectController's contentObject to MyObject's "thing2".

In MyObject, in code, set MyObject's "thing2" to @"howdy". Sure enough, the
NSObjectController's content is also @"howdy". So the binding is working in
this direction.

No, in code, set NSObjectController's content (using setContent:) to
@"byebye". Back in MyObject, "thing2" is still @"howdy"! So even this, a
binding established in the standard way, in IB, between a controller and a
model object, is only one-way!!

But wait, there's more!!! Instead of using setContent:, use addObject: to
set the NSObjectController's content value to @"byebye". Now the binding
suddenly works in the other direction - MyObject's "thing2" is now
@"byebye"! So this is a major difference between addObject: and setContent:,
even though the docs say that for NSObjectController they are synonyms.

<http://developer.apple.com/documentation/Cocoa/Conceptual/CocoaBindings/Con
cepts/CntrlContent.html#//apple_ref/doc/uid/TP40002147-183285-BBCDFJHD>

m.

--
matt neuburg, phd = <email_removed>, <http://www.tidbits.com/matt/>
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