Productivity by a thousand cuts: The Kotlin Way

Transcript

1. THE KOTLIN WAY
   PRODUCTIVITY BY A THOUSAND CUTS…
   david@http4k.org
   @daviddenton
   

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2. WHO THE HELL IS THIS GUY?
   HI, I’M DAVID
   

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3. WHO THE HELL IS THIS GUY?
   HI, I’M DAVID
   ENGINEERING LEAD
   

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4. WHO THE HELL IS THIS GUY?
   HI, I’M DAVID
   ENGINEERING LEAD
   OPEN SOURCE
   

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5. WHO THE HELL IS THIS GUY?
   HI, I’M DAVID
   ENGINEERING LEAD
   OPEN SOURCE
   SPEAKER
   

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6. WHO THE HELL IS THIS GUY?
   HI, I’M DAVID
   ENGINEERING LEAD
   OPEN SOURCE
   SPEAKER
   TRAINER
   

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7. INTO THE MELTING POT
   “GOOD ARTISTS BORROW.
   GREAT ARTISTS STEAL.”
   - PABLO PICASSO
   

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8. - PABLO PICASSO
   INTO THE MELTING POT
   “GOOD ARTISTS BORROW.
   GREAT ARTISTS STEAL.”
   - TS ELIOT
   

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9. - PABLO PICASSO
   INTO THE MELTING POT
   “GOOD ARTISTS BORROW.
   GREAT ARTISTS STEAL.”
   - TS ELIOT
   “IMMATURE POETS IMITATE;
   MATURE POETS STEAL.”
   

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10. INTO THE MELTING POT
    “GOOD LANGUAGES BORROW.
    GREAT LANGUAGES STEAL.”
    - ME, ABOUT KOTLIN
    

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11. INTO THE MELTING POT
    

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12. val myValue: Int = null
    operation(myValue.toString())
    FIVE THINGS YOU’LL LOVE ABOUT KOTLIN
    1. NULL SAFETY
    ▸ Nulls: The Billion Dollar Mistake
    ▸ Kotlin builds null safety into the type system
    ▸ Hard to subvert it in your own code
    

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13. val myValue: Int = null
    operation(myValue.toString())
    val myValue: Int = null
    operation(myValue.toString())
    val myValue: Int? = null
    operation(myValue?.toString() ?: “default”)
    FIVE THINGS YOU’LL LOVE ABOUT KOTLIN
    1. NULL SAFETY
    ▸ Nulls: The Billion Dollar Mistake
    ▸ Kotlin builds null safety into the type system
    ▸ Hard to subvert it in your own code
    

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14. fun File.readText() = InputStreamReader(
    FileInputStream(this))
    .use { StringWriter()
    .apply { it.copyTo(this)}.toString() }
    val text = File("content").readText()
    FIVE THINGS YOU’LL LOVE ABOUT KOTLIN
    2. EXTENSION FUNCTIONS
    ▸ Extend types you don’t own! (And ones you do!)
    

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15. fun File.readText() = InputStreamReader(
    FileInputStream(this))
    .use { StringWriter()
    .apply { it.copyTo(this)}.toString() }
    val text = File("content").readText()
    fun File.readText() = InputStreamReader(
    FileInputStream(this))
    .use { StringWriter()
    .apply { it.copyTo(this)}.toString() }
    val text = File("content").readText()
    FIVE THINGS YOU’LL LOVE ABOUT KOTLIN
    2. EXTENSION FUNCTIONS
    ▸ Extend types you don’t own! (And ones you do!)
    

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16. FIVE THINGS YOU’LL LOVE ABOUT KOTLIN
    3. SENSIBLE CONCISENESS
    ▸ Immutable by default
    ▸ Type inference
    ▸ Data classes
    ▸ Trailing Lambdas
    ▸ Infix functions & Operators
    ▸ DSLs
    fun ChatApp(): PolyHandler {
    val userCounter = AtomicInteger()
    val messages = mutableListOf()
    val participants = ConcurrentHashMap()
    fun addMessage(new: String) {
    messages.add(new)
    participants.values.forEach { it.send(WsMessage(new)) }
    }
    fun newConnection(ws: Websocket) {
    val id = "user${userCounter.incrementAndGet()}"
    participants += id to ws
    messages.map(::WsMessage).forEach { ws.send(it) }
    addMessage("$id joined")
    ws.onMessage { addMessage("$id: ${it.bodyString()}") }
    ws.onClose {
    participants -= id
    addMessage("$id left")
    }
    }
    val http = BasicAuth("http4k",
    Credentials("kotlin", “isgreat"))
    .then(static(Classpath()))
    val ws = websockets("/ws" bind ::newConnection)
    return PolyHandler(http, ws)
    }
    fun main() {
    ChatApp().asServer(Jetty(5000)).start()
    }
    

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17. FIVE THINGS YOU’LL LOVE ABOUT KOTLIN
    4. KOTLIN EVERYWHERE!
    

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18. FIVE THINGS ABOUT KOTLIN YOU’LL LOVE
    5. THE 100S OF OTHER THINGS, INCLUDING…
    ▸ Really easy to learn
    ▸ Idea automatically converts Java to Kotlin!
    ▸ Awesome standard library
    ▸ Language is Open Source
    ▸ Seamless Java Interop
    ▸ Friendly community
    ▸ Both Developers and OSS maintainers absolutely love Kotlin!
    

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19. ONE THING ABOUT KOTLIN YOU’LL HATE
    1. A WARNING
    YOU MAY NOT WANT TO GO BACK
    

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20. FIN
    #thanks!
    david@http4k.org
    @daviddenton
    

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