On 10 Jan 2011, at 11:42 PM, Kenneth Baxter wrote: > Hi, I have a project I'm working on which needs to run on 10.5 and 10.6. I > have various things enabled or disabled using: > > if (floor(NSAppKitVersionNumber) > NSAppKitVersionNumber10_5) ... > > but I also have some places in my code where I want to use a CAShapeLayer > subclass in 10.6 and an alternate version based on NSViews in 10.5. My logic > says it is not going to call the CAShapeLayer, but it appears that it has > been linked in to the application anyway, so when I try to run the program on > 10.5, it gives me the error: > > dyld: Symbol not found: _OBJC_CLASS_$_CAShapeLayer > > What is the proper way to handle situations where a whole class is missing in > the earlier SDK like this? The documentation doesn't seem to address this > scenario as far as I can see.
You might be able to weakly link the class, in which case dyld will not complain but messages to CAShapeLayer will return nil. I don't remember on which OS revs it became possible to weak link a class, though. (Weak linking C symbols has been possible since 10.2; see TN2064.) The older technique is to avoid class-name literals and use NSClassFromString() to get a reference to the class object: Class shapeLayer = NSClassFromString(@"CAShapeLayer"); blahblah = [[shapeLayer alloc] init...]; If CAShapeLayer isn't linked into your process, then NSClassFromString() will safely return Nil. You can test for that or you can check NSAppKitVersionNumber. _______________________________________________ Cocoa-dev mailing list ([email protected]) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to [email protected]
