Re: Are runtimes of system objects dynamic/SDK dependent/whatever?
Re: Are runtimes of system objects dynamic/SDK dependent/whatever?
- Subject: Re: Are runtimes of system objects dynamic/SDK dependent/whatever?
- From: Saagar Jha via Cocoa-dev <email@hidden>
- Date: Tue, 14 Jun 2022 14:17:30 -0700
Option 2 is pretty much what happens. In addition, the behavior of doCoolStuff
might change in 11.0 versus 10.15; the system framework will pick between the
two by checking which SDK you were linked against.
> On Jun 14, 2022, at 12:30, Aandi Inston via Cocoa-dev
> <email@hidden> wrote:
>
> I'm trying to understand how Mac OS X actually implements the predefined
> objects like NSApplication. Not in detail by function, but where the code
> lives. This is by way of understanding what happens if the SDK version
> doesn't match the system version. Let's suppose I would like to use an
> imaginary method [NSApplication doCoolStuff] which was added in Mac OS
> 10.15, but I'm linking with the 10.14 SDK.
>
> So, where does doCoolStuff actually exist? I can think of several
> possibilities.
>
> 1. The code for NSApplication and its methods is linked entirely into my
> application. This makes it self contained, though it might depend on system
> calls and external services. So NSApplication exists inside my application,
> and it runs the version written as part of the SDK I link with (10.14).
> There is no way for me to call [NSApplication doCoolStuff] , because it
> doesn't exist in the NSApplication I am using (10.14 runtime).
>
> 2. The code for NSApplication is dynamically linked from system-provided
> shared code of some kind, using the same code regardless of the SDK version
> used. The shared code may include some differences according to info it has
> on the SDK used to build the current app. In this case perhaps I could call
> [NSApplication doCoolStuff], though not by coding that; something involving
> NSSelectorFromString.
>
> 3. The code for NSApplication is dynamically linked from system-provided
> shared code of some kind, using code dependent on the SDK version used. The
> methods provided will depend on the SDK version used. This would imply
> that, like case 1, is no way for me to call [NSApplication doCoolStuff] ,
> because it doesn't exist in the NSApplication runtime I am using.
>
> 4. The code for NSApplication is a stub to some other kind of external
> interface I never heard of...
>
> Thanks in advance!
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