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Limited import clarification
and its effect
try! Swift Tokyo 2019
Tomoya Hirano @DeNA
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Import
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Import Declaration
1. attributes import module
2. attributes import module.submodule
3. attributes import importKind module.symbolName
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Import Declaration
1. attributes import module
2. attributes import module.submodule
3. attributes import importKind module.symbolName
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1. Attributes
• Specify how to import symbols
• Optional
• @testable / @_exported
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@testable
• For testing and development.
• Import internal methods as public.
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@_exported
• Import symbols as own code
• Undocumented attributes
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2. Submodule import
1. attributes import module
2. attributes import module.submodule
3. attributes import importKind module.symbolName
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Example: SceneKit initializer
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Example: SceneKit initializer
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3. Kind import
1. attributes import module
2. attributes import module.submodule
3. attributes import importKind module.symbolName
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struct class enum protocol
typealias func let var
3. Kind import
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3. Kind import
• Individual import is only top-level
• Cannot import overloaded functions separately
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Example: Conflict method name
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No content
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1. Attributes
2. Submodule import
3. Kind import
Import Options
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Can the build time be shortened?
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4. Measuring the build times
• made 100,000 methods
• import Core vs import func Core.function0
• Tried 10 times
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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
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Basic Import Kind Import
Filesize 7336KB 7336KB
Md5
0b10a59ce0a75decbb
2f120520c4fbc1
0b10a59ce0a75decbb
2f120520c4fbc1
Binary size
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Build time Binary Size Namespace
Simple Import Same Same Optional
Kind specify Same Same Necessary
Pros & Cons