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Conversely, will existing Obj-C (and hybrid Swift/Obj-C) apps be able to call the new Swift Foundation? And will it be binary-compatible with existing apps, or

Conversely, will existing Obj-C (and hybrid Swift/Obj-C) apps be able to call the new Swift Foundation? And will it be binary-compatible with existing apps, or will Apple just ship a separate compatibility version of Foundation for use by legacy apps?

saagarjha 4y ago
Yes, it’ll be binary compatible.
- bsaul 4y ago
  i don't understand how a compiled language like swift can be binary compatible with a dynamic one like objc. How are they going to implement method swizzling on NSObject for example ?
  - Reason077 4y ago
    Swift and Obj-C are both compiled languages, and also dynamic in the sense that they allow a lot of runtime introspection and dynamic dispatch. They're already binary compatible, in the sense that you can call compiled Obj-C classes from Swift apps (of course), and also - with some restrictions - call compiled Swift code from Obj-C. In fact, you can "swizzle" methods in Swift just like in ObjC, on classes derived from NSObject: https://medium.com/@valsamiselmaliotis/method-swizzling-in-swift-2ff25926569d https://medium.com/@valsamiselmaliotis/method-swizzling-in-s...
    - bsaul 4y ago
      What you’re doing in this medium post is call the objc runtime from swift and take advantage from swift <-> objc bridging. This does not work if the class you’re trying to swizzle is a pure swift class. For a reason : swift is mostly static dispatch, whereas objc is pure dynamic dispatch (taking its root from smalltalk). This means code that tried to swizzle foundation types, assuming foundation is developped in objc, will not work anymore once foundation is using a pure swift implementation.
      - Reason077 4y ago
        If Foundation is to retain binary compatibility with Obj-C, then it will by necessity still be using the Obj-C runtime, with Foundation types still extending NSObject, and thus swizzling should still work as before. The alternative would be for Apple to break compatibility with old Obj-C apps, instead shipping a compatibility version of Foundation.framework which old apps would continue to link against. But it sounds like they're not going that route.
        bsaul 4y ago
        Yet using the objc runtime defeats the purpose of being easier to port to other platforms.

saagarjha 4y ago

Yes, it’ll be binary compatible.

bsaul 4y ago
i don't understand how a compiled language like swift can be binary compatible with a dynamic one like objc. How are they going to implement method swizzling on NSObject for example ?
- Reason077 4y ago
  Swift and Obj-C are both compiled languages, and also dynamic in the sense that they allow a lot of runtime introspection and dynamic dispatch. They're already binary compatible, in the sense that you can call compiled Obj-C classes from Swift apps (of course), and also - with some restrictions - call compiled Swift code from Obj-C. In fact, you can "swizzle" methods in Swift just like in ObjC, on classes derived from NSObject: https://medium.com/@valsamiselmaliotis/method-swizzling-in-swift-2ff25926569d https://medium.com/@valsamiselmaliotis/method-swizzling-in-s...
  - bsaul 4y ago
    What you’re doing in this medium post is call the objc runtime from swift and take advantage from swift <-> objc bridging. This does not work if the class you’re trying to swizzle is a pure swift class. For a reason : swift is mostly static dispatch, whereas objc is pure dynamic dispatch (taking its root from smalltalk). This means code that tried to swizzle foundation types, assuming foundation is developped in objc, will not work anymore once foundation is using a pure swift implementation.
    - Reason077 4y ago
      If Foundation is to retain binary compatibility with Obj-C, then it will by necessity still be using the Obj-C runtime, with Foundation types still extending NSObject, and thus swizzling should still work as before. The alternative would be for Apple to break compatibility with old Obj-C apps, instead shipping a compatibility version of Foundation.framework which old apps would continue to link against. But it sounds like they're not going that route.
      - bsaul 4y ago
        Yet using the objc runtime defeats the purpose of being easier to port to other platforms.