The document discusses how a mobile developer at LINE Fukuoka uses Python for code inspection and generation in their iOS app project called LINE Creators Studio. Python scripts are used to detect unused files, generate Swift code for internationalization and analytics event tracking, and more. The developer advocates for using type-safe languages and code generation tools like SwiftGen to get the benefits of dynamic scripting while maintaining type safety.

1. Python for Swift
/ LINE Fukuoka
2018/8/22, LINE Developer meetup in Kyoto #43

2. ● iOS Developer at LINE Fukuoka
● Project: LINE Creators Studio
Self introduction

3. ● iOS Developer at LINE Fukuoka
● Project: LINE Creators Studio
Self introduction
Today’s topic

4. ● Inspection (find unused file, etc)
● Code generation
We use Python for two purposes

5. ● Inspection (find unused file, etc)
● Code generation
We use Python for two purposes
Today’s topic

6. There is a common saying
among
Swift developers

7. Good implementation produces
compilation error
before running with problem

8. ● Any string values are acceptable as filename
Cause of runtime error
For example…
read(“path/to/file”)
send(“v2”)
● When you want to send version
● “2”, ”ver2” are acceptable, and caller must assure the input

9. ● Any string values are acceptable as filename
Cause of runtime error
For example…
read(“path/to/file”)
send(“v2”)
● When you want to send version
● “2”, ”ver2” are acceptable, and caller must assure the input
Runtime Error

10. ● Any string values are acceptable as filename
Cause of runtime error
Solutions
read(“path/to/file”)
send(“v2”)
● When you want to send version
● “2”, ”ver2” are acceptable, and caller must assure the input
Android generates R, and we can write like `R.id.filename`
Define original types like enum (※constant string is not enough)

11. ● A code generator like R of Android
● Variable asset is Asset type, and we cannot use String, etc…
● Also we can use for Font, Color, Localizing, …
https://github.com/SwiftGen/SwiftGen
SwiftGen

12. "lfk" = "LINE Fukuoka ";
"meetup.name" = “Developer Meetup #%d";
"meetup.themeis" = " %@";
enum L10n {
/// LINE Fukuoka
static let lfk = L10n.tr("localizable", "lfk")
enum Meetup {
/// LINE Developer Meetup #%d
static func name(_ p1: Int) -> String {
return L10n.tr("localizable",
"meetup.name", p1)
}
/// %@
static func themeis(_ p1: String) -> String {
return L10n.tr("localizable",
"meetup.themeis", p1)
}
}
}
$ swiftgen strings -t dot-syntax-swift3 path/to/file
SwiftGen output example

13. ● Dependency Injection / @_ishkawa
iOSDC2017
● Safety + Easiness
Is the best thing to do
for Swift

14. ● Tool for code generation by Apple
● used in apple/swift repository
● uses Python
gyb
https://github.com/apple/swift/blob/2a25a8c14fecaaca68d881fcbcba71a85bcc1e9d/validation-test/stdlib/ArraySlice.swift.gyb

15. ● 100+ Analytics events defined on Wiki
● We have to copy&paste these all?
Motivation

16. ● Parse HTML Table
● Generate Swift code
Specifications
track(AnalyticsEvent.ScreenA.event1)

17. https://qiita.com/_ha1f/items/f318e1614edb6b08ac3f
Please refer Qiita for detail!

18. ● Types help as to be safe!
● Writing small scripts with shell, Python is good…
● We have to write without types to be typed? No! You can use
Swift + Sourcery if you have enough time!
Conclusion

19. LINE Fukuoka
@_ha1f
https://github.com/ha1f

20. THANK YOU