On Aug 15, 2011, at 10:38 AM, Martin Hewitson wrote:
> I guess this is a really simple question to answer, but somehow my googling
> doesn't lead me to it.
>
> I have an app and I want to include NSPopovers when the app runs on Lion. I
> have some run-time way of finding out if it is Lion or not (see below), but
> when the app runs on 10.6 I get errors like:
>
> Symbol not found _OBJC_CLASS_$_NSPopover
>
> I have the deployment target set to 10.6 in Xcode and the base sdk set to
> 10.7.
>
> Am I doing something wrong? Is it possible to do what I want to do?
What compiler are you building with? Clang should automatically weak-link this
class for you, but GCC (and GCC-LLVM) don't know how to do so and as such you
would need to use NSClassFromString() to obtain the NSPopover class instead of
referencing it directly.
In either case, the best general way to determine availability of weak-linked
implementations is to test for them directly rather than using a system version
check (like gestalt). If your using Clang (which I suspect you are not given
your error) you could just use:
"if ([NSPopover class]) { /* do stuff with popovers */ } else { /* do stuff
without */ }"
In GCC you should use
Class nsPopover = NSClassFromString(@"NSPopover");
if (nsPopover) ...
--
David Duncan
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