Limited import clarification and its effect/tryswift2019

Import is able to explicitly specify submodules or specific elements.In this session, I will review the specifications of these imports and consider the impact on binary size and performance.

1. Limited import clarification and its effect try! Swift Tokyo 2019 Tomoya Hirano @DeNA
2. Import
3. Import Declaration 1. attributes import module 2. attributes import module.submodule 3. attributes import importKind module.symbolName
4. Import Declaration 1. attributes import module 2. attributes import module.submodule 3. attributes import importKind module.symbolName
5. 1. Attributes • Specify how to import symbols • Optional • @testable / @_exported
6. @testable • For testing and development. • Import internal methods as public.
7. @_exported • Import symbols as own code • Undocumented attributes
8. 2. Submodule import 1. attributes import module 2. attributes import module.submodule 3. attributes import importKind module.symbolName
9. Example: SceneKit initializer
10. Example: SceneKit initializer
11. 3. Kind import 1. attributes import module 2. attributes import module.submodule 3. attributes import importKind module.symbolName
12. struct class enum protocol typealias func let var 3. Kind import
13. 3. Kind import • Individual import is only top-level • Cannot import overloaded functions separately
14. Example: Conflict method name
16. 1. Attributes 2. Submodule import 3. Kind import Import Options
17. Can the build time be shortened?
18. 4. Measuring the build times • made 100,000 methods • import Core vs import func Core.function0 • Tried 10 times
19. Basic Import Kind Import Average 277.645s 285.105s(+7.64s) Max 309.46s 312.99s(+3.53s) Min 273.48s 265.25s(-8.23s) Build time
20. Basic Import Kind Import Filesize 7336KB 7336KB Md5 0b10a59ce0a75decbb 2f120520c4fbc1 0b10a59ce0a75decbb 2f120520c4fbc1 Binary size
21. Build time Binary Size Namespace Simple Import Same Same Optional Kind specify Same Same Necessary Pros & Cons