Building Swift Static Libraries

Transcript

1. Building Swift Static Libraries Samuel Giddins 1
2. @segiddins Mobile Developer Experience @ Square CocoaPods Core Contributor 2 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
3. Mobile Developer Experience ⇢Owns the build system, dependency manager, interface with CI ⇢Maintains the (open source) tools used to build the app ⇢Keeps developers as productive as possible ⇢Cross platform: iOS & Android ⇢Develops CocoaPods features 3 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
4. CocoaPods @ Square ⇢265 total pods ⇢Swift, Objective-C ⇢Dynamic Frameworks, Static Libraries, Static Frameworks ⇢Monorepo & Multirepo 4 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
5. A (Brief) History of Swift Linkage ⇢SwiftyThing.framework From Xcode ⇢ SwiftyThing (as a dynamic library) ⇢libSwiftyThing.a From Swift PM ⇢... And that's it! 5 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
6. Until Xcode 9 6 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
7. Xcode 9 added the ability to build Swift into static libraries 7 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
8. Why static libraries? ⇢Easier to obfuscate / strip dead code ⇢No overhead on app launch ⇢Possible to have true single-file executables 8 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
9. Aside: This also means you can now build Swift static frameworks, if you like! 9 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
10. What static libraries don't fix: ⇢ABI stability ⇢Module format stability ⇢Clang Modules ⇢Swift compiler performance ⇢Buggy code 10 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
11. But: They did allow us to start building Swift pods 11 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
12. So, how do these magic new libraries work? 12 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
13. Swift Static Libraries, In Practice 13 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
14. Swift Static Libraries, In Practice Surprisingly simple! 1. Create an app / command line target 2. Create a static library target 1. Delete Objective-C files 2. Add a Swift file 3. Link the static library into the app 4. Build & Run 5. Profit‽ 14 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
15. But: Only if you don't want to use any of the code in the static library in another target 15 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
16. So, no profit. 16 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
17. The hardest part of building Swift static libraries has been using them 17 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
18. Frameworks make importing Swift code easy 18 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
19. Importing Swift Code 1. .modulemap 2. Headers 3. .swiftmodule 4. Generated -Swift.h Bridging Header 19 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
20. Importing Swift Code Objective-C: $ clang -F path/to/framework -f FrameworkName ... Swift: $ swiftc -F path/to/framework -f FrameworkName ... 20 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
21. Importing Swift Code Piece of cake with frameworks! (Seriously, frameworks are amazing) 21 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
22. On the other hand: Static librarys Manual integration 22 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
23. Aside: Most of this is all trivia I learned integrating Swift static library support into CocoaPods. If I could do it all again, I would've just made static frameworks work and call it a day. 23 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
24. Now entering: Compiler 24 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
25. Compilers Magic But constructing correct compiler arguments by hand is tedious and error prone and it's 2018 and no one should ever need to do it 25 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
26. ⚠ Detour into Clang Modules 26 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
27. ! I gave a talk about this particular, highly painful, subject at try! Swift Tokyo 2018 27 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
28. Clang Modules & Swift Modules are highly related 28 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
29. For Swift to import Objective-C: ⇢Bridging Header ! ⇢Modules for the imported code For Objective-C to import Swift: ⇢Directly import generated -Swift.h header ⇢Import the generated module 29 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
30. Seeing a pattern here? 30 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
31. Modules are the lingua franca by which Swift and Objective-C are meant to bridge 31 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
32. Modules are created automatically when building frameworks in Xcode 32 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
33. This is where the heavy lifting comes in for manually integrating static libraries 33 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
34. Clang: $ clang -fmodule-map-path=path/to/Library.modulemap Swift: $ swiftc -Xcc -fmodule-map-path=path/to/Library.modulemap -I dir/of/other/library.swiftmodule 34 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
35. This is what enables imports to work Objective-C: @import Library; Swift: import Library 35 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
36. Why does being able to use imports matter? ⇢It allows libraries to import other libraries ⇢It gets rid of buggy bridging headers ⇢Modular imports are semantic, and don't need to be tied to particular header names 36 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
37. How do I mix Swift & Objective-C in one library? 37 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
38. How do I mix Swift & Objective-C in one library? Trivial with frameworks. ⇢Objective-C headers in the module map are immediately usable from Swift ⇢#import <Library/Library-Swift.h> from Objective-C 38 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
39. How do I mix Swift & Objective-C in one library? ⇢Pass the module map to both clang & swiftc ⇢Pass the path to the generated Objective-C interface to clang ⇢Experience all new compiler segfaults 39 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
40. Your developers were so preoccupied with whether or not they could, they didn't stop to think if they should. — Jurassic Park 40 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
41. Should I... ⇢Mix Swift & Objective-C? ⇢Mix static libraries & dynamic frameworks? ⇢Mix static libraries & static frameworks? 41 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
42. But Samuel, what if that looks like a lot of work? 42 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
43. Never fear! We're programmers, so we have pre-written solutions! 43 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
44. Pre-written solutions: ⇢Swift Package Manager ⇢CocoaPods ⇢ ❌ Xcode 44 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
45. In CocoaPods 45 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
46. In CocoaPods ⇢Released in v1.5 ⇢Mixed Swift / Objective-C libraries ⇢Objective-C & Swift can both import from Swift static libraries ⇢Just remove use_frameworks! ⇢You're ! good to go 46 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
47. Known Rough Edges ⇢Mixing (precompiled) bridging headers & modules ⇢Swift autocomplete ⇢The path of the Swift generated interface to import ⇢Too many compiler flags ⇢None of this was meant to work in this way. ⇢At all. 47 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
48. So, Samuel, if it's all so terrible, why did you add support in CocoaPods and start using it at work? 48 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
49. We didn't know what we were getting into. Honestly. 49 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
50. Swift is the Future 50 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
51. Swift is the Future Being able to write it now, and write libraries with Swift, is worth the tradeoff. It's better than developing a massive hairball or ignoring the future of  platform development. 51 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
52. What's next? 52 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018
53. Samuel Giddins @segiddins 53 — Building Swift Static Libraries – Samuel Giddins @ iOS Dev Camp DC 2018