Hey Brent, thanks that helps. This leads me to one more question.
Let's say I build my framework with two versions, A and B - A is the
base and B includes only the 10.6 features.
Is there a way in xcode to specifically tell the linker that it's it's
linking against A or B? The reason I ask is because in xcode when you
link against a framework you just tell it to link against a
".framework" folder. But How can tell the loader to load a specific
version (A or B) without having to modify the "current" symlink in the
.framework folder?
If I can accomplish this, then I can create two build targets. Each
just building either A or B, but then when I link against the
framework I can have it link A or B. Does that make sense?
Thanks
On Tue, Sep 8, 2009 at 3:25 PM, Brent Gulanowski<bgulanow...@gmail.com> wrote:
> For classes, you can check whether NSClassFromString(@"Classname") returns a
> class.
> For selectors, you can check whether NSSelectorFromString(@"selector")
> returns a selector.
> Usually that's enough. In fact, if you pick a representative class that was
> introduced in the OS release of your choice, you can use that as a short cut
> to check for the OS version. Or you can check the version major and minor
> values using Gestalt for accurate version info:
> file:///Developer/Documentation/DocSets/com.apple.adc.documentation.AppleSnowLeopard.CoreReference.docset/Contents/Resources/Documents/documentation/Carbon/Reference/Gestalt_Manager/Reference/reference.html
>
> enum {
> gestaltSystemVersion = 'sysv'
> gestaltSystemVersionMajor = 'sys1',
> gestaltSystemVersionMinor = 'sys2',
> gestaltSystemVersionBugFix = 'sys3'
> };
>
> (Those symbols should link right into the file in your docs.)
> Now, that's pretty awkward because you won't be able to instantiate a class
> without converting from the classname or send a message without converting
> the method sig and calling -performSelector: so I'd think the right way
> would be to build two different versions of your framework and ship them
> separately, making sure to version them so they can co-exist if necessary.
> Not that hardly anyone does that.
>
> On Tue, Sep 8, 2009 at 12:24 AM, aaron smith
> <beingthexemplaryli...@gmail.com> wrote:
>>
>> Hey All,
>>
>> I've got a framework (GDKit) that I maintain - started writing it on
>> 10.5. I'm running into something I'm not sure how to handle.
>>
>> -So far, everything I've been writing in GDKit links against 10.5, and
>> applications I've been writing link against GDKit, and 10.5.
>> -I have some new classes I want to add to the framework, but some of
>> the API's are in 10.6 only.
>> -The new classes and features in my framework are optional - because
>> they require 10.6, but I don't want to have to change all of my
>> applications to require 10.6.
>
> It is possible to build a framework against a different version of the OS
> than an application that depends on it. Although you have to be careful
> about setting up dependencies in Xcode which might push build settings from
> the app down to the framework, if you use that feature of Xcode.
>
>>
>> What I'm trying to figure out is how to keep the framework compiling
>> for 10.5, but optionally including the new features/classes when it's
>> compiling for 10.6.
>>
>> There's just a few things I'm unclear of..
>>
>> -When it's compiling for 10.5, can I completely exclude files from
>> compiling (the 10.6 features)? Is that the right way to exclude
>> features?
>
> Well it seems you're definitely going to have to build two versions of the
> framework (probably by creating two different build configurations) -- in
> the 10.5, yes, you won't compile/link those classes which require 10.6.
>
>>
>> -When I link against GDKit from an application, how can I have the app
>> link against GDKit that include only the 10.5 features? Or optionally
>> link against the build that includes the 10.6 features?
>
> The linking is done dynamically. If you want the same compiled version of
> your app to use different features of your framework depending on where it
> is and what's available, it will have to explicitly check for the existence
> of those things. Your app should just link against the framework, not a
> specific version of it (if you choose to use versions).
> If it all becomes too onerous to access 10.6-only classes/methods using
> NSStringFrom... (or, in the case of Carbon/C, some other approach), you
> would be better off building separate versions of your app.
>
>>
>> I've been reading about framework versioning, and what they recommend
>> is creating a new major version. But that doesn't really help my
>> problem - as creating a new major version would require the 10.6 SDK.
>> Hopefully that makes sense.
>>
>> Does anyone know of any blog posts or tutorials about this particular
>> situation?
>>
>> Any ideas would be sweet.
>> _______________________________________________
>
> I'm no expert in targetting multiple OS versions simultaneously, but these
> are the strategies we use here. Hopefully this will help. (If I've made any
> errors, I expect they'll get corrected.)
>
> --
> Brent Gulanowski
>
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