Let's check out Clikt - Speaker Deck

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Clikt brian plummer @plummermakes

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Command Line Interface for Kotlin

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/giphy ain’t nobody got time for that

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Clikt does one job really well

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Options and Arguments

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val count by option()

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val count by option().default(“1”)

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val count: Int by option().int().default(1)

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option(help = “Number of greetings”)

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val name by argument()

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val name by argument(help = “name to say hello to”)

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val someFlag by option()

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val someFlag by option().flag()

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val someFlag by option(“-f”).flag()

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val someFlag by option (“-f”).flag(default = false)

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./cliktsample brian Flag f has value: false Hello brian!

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./cliktsample -f brian Flag f has value: true Hello brian!

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How do we get that binary? ./cliktsample

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Gradle’s application plugin

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./gradlew installDist ./build/install/cliktsample/bin/ clicktsample

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Packages us up nicely!

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Lots of features! Let’s look at just a couple more

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Custom Types

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Multiple Options

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Nested Commands

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Prompt for input val name by option().prompt()

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Prompt for password prompt(requireConfirmation = true, hideInput = true)

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And much much more •Choice / Mutually Exclusive / Eager /……Options •Documenting / Formatting •Token normalization / Replacing stdin/stdout •Launch Editor / Bash Autocomplete •Exception Handing

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And much much more

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Why not a Kotlin lib like kotlin-argparse or kotlinx.cli? •Lack of subcommand, though that has changed •Not nearly as feature rich •Clikt tries to be consistent and intuitive •Clikt is JVM based

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Sometimes we have to support scripts that we would rather not

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There was a ruby script that did string interpolation

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Legacy Kotlin

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We can now •Isolate the legacy code •Better control on legacy code invocation •Build new features on our terms •Refactor and pull code into Kotlin

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StranglerFig Application •Martin Fowler ~ 2004 •Create new system around the old •Gradually move functionality to new •Less risky way to replace

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Thanks! @plummermakes