Leopard-specific functionality in non-Leopard -only project

FROM : Jacob Bandes-Storch
DATE : Sat Jun 21 21:51:02 2008

I'm working on a project (with another developer) that will target 
OSes older than 10.5, and I'd like to use the Leopard-only NSWindow 
method -setCollectionBehavior:. As far as I know, the best way to do 
this is to check for the method using -respondsToSelector:. I need to 
use the enum type NSWindowCollectionBehavior. When I try this, I get 
an error saying "error: 'NSWindowCollectionBehaviorCanJoinAllSpaces' 
undeclared (first use in this function)" and a warning "warning: 
'NSWindow' may not respond to '-setCollectionBehavior:'". This is 
because I'm using the 10.4 SDK... I've read in some places to set the 
"Cross-develop using target SDK" setting of the project to 10.5, but 
that setting is not available in the General tab of the project info. 
Does anyone know how to do this properly without angering the compiler?