On Aug 28, 2008, at 10:15 PM, Sherm Pendley wrote:
On Thu, Aug 28, 2008 at 9:56 AM, Roland King <[EMAIL PROTECTED]> wrote:
I tried that before, making my protocol inherit from the NSObject
Protocol and it sort of worked, but not quite.
Protocols aren't inherited. You can inherit an implementation of the
NSObject protocol, by writing a subclass of the NSObject class, but
that's a very different animal.
let me use Apple's terminology instead of my own sloppy one, you can
'incorporate' other protocols into your own, so my first shot was
@protocol Foo <NSObject>
but that fails addObserver:... if you use (id<Foo>) as addObserver:..
isn't part of NSObject so what I wanted was
@protocol Foo <NSObject, NSKeyValueObserving>
but NSKeyValueObserving isn't really defined so you can't do that
I don't quite understand why protocols like NSKeyValueObserving
aren't formalized and in a .h file somewhere so you could just use
them in the same way you can the NSObject protocol. They're
documented, why not just write the .h file. There's probably a very
good reason for it which has totally escaped me.
Conforming to a protocol is an all-or-nothing affair - you have to
implement *all* of the protocol's methods. The informal protocols
I'm aware of tend to have one or more optional methods.
You can have @optional Protocol methods (is that new, that may be new,
I'm really not sure). Of course if the protocols ended up all optional
then indeed that would rather defeat the purpose of the whole thing.
That's a very good point though. I'm still more used to interfaces in
other languages which really are all-or-nothing.
sherm--
--
Cocoa programming in Perl: http://camelbones.sourceforge.net
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