Homo Kotlin, a brief History of Kotlin in Agoda - Speaker Deck

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HOMO KOTLIN A brief History of Kotlin Development in Agoda

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COGNITIVE REVOLUTION 70,000 BC

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.subscribe(result -> { saveId(); }, error -> { displayError(); });

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*.class Java complier

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*.dex *.class Java complier application.apk

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*.dex *.class Java complier Kotlin complier application.apk

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*.dex *.class Java complier Kotlin complier application.apk :app:compileDebugKotlin :app:compileDebugJavaWithJavac

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fun String.isThaiCharacter(): Boolean

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fun String.isThaiCharacter(): Boolean public final class Extension { public static final boolean isThaiCharacter(@NotNull String $var) }

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data class Player( val id: Int, val name: String, var level: Int)

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data class Player( val id: Int, val name: String, var level: Int)

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data class Player( val id: Int, val name: String, var level: Int)

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data class Player( val id: Int, val name: String, var level: Int)

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data class Player( val id: Int, val name: String, var level: Int)

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data class Player( val id: Int, val name: String, var level: Int) public String toString() { return "Player(id=" + this.id + ", name=" + this.name + ", level=" + this.level + ")"; }

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public static final int USER = 1;

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public static final int USER = 1; interface Player { fun name(other: T): String fun upgradePlayer(): R }

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public static final int USER = 1; sealed class Error { object UserNotFound : Error() object ExpiredSession : Error() } interface Player { fun name(other: T): String fun upgradePlayer(): R }

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public static final int USER = 1; sealed class Error { object UserNotFound : Error() object ExpiredSession : Error() } interface Player { fun name(other: T): String fun upgradePlayer(): R } private inline fun perform

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AGRICULTURAL REVOLUTION 4000 BC 70,000 BC

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Why Testing?

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> 10k Test cases > 1000 ATs Why Testing?

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• More readable test code • Explore Kotlin features Goals:

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• More readable test code • Explore Kotlin features Goals:

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View Actions View Matchers View Assertions

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open class VActions { fun click() = ViewActions.click() … } open class VAssertions { fun isNotEnabled() = ViewAssertions.matches(not(isEnabled())) fun doesNotExist() = ViewAssertions.doesNotExist() … }

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fun expectToBeVisible() { interaction(vm.viewPageContent, va.isDisplayed()) }

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• Lots of interesting features • Still not reach our goals!! What we found so far:

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• Lots of interesting features • Still not reach our goals!! What we found so far: LET’S EXPLORE MORE!!!

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High-order functions

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High-order functions “a function that takes functions as parameters, or returns a function”

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class HTML() { fun body(Body.() -> Unit) { ... } }

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class HTML() { fun body(Body.() -> Unit) { ... } } fun html(HTML.() -> Unit) { ... }

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class HTML() { fun body(Body.() -> Unit) { ... } } fun html(HTML.() -> Unit) { ... } html { body { ... } }

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So, what can we do about it?

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fun expectToBeVisible() { interaction(vm.layout, va.isDisplayed()) }

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fun expectToBeVisible() { screen { layout { isDisplayed() } } } fun expectToBeVisible() { interaction(vm.layout, va.isDisplayed()) }

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• Start to create essential matchers/actions/assertions • Convert some of our PageObject classes How we start?

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class OccupancyPageKt { val screen = OccupancyScreen() fun shouldBeVisible() { screen { layout { isDisplayed() } } } fun shouldSeeGuestsAndRoomLabel() { screen { guestAndRoomLabel { isDisplayed() } } }

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Finally, we share effort to the world!!

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Our main contributor Ilya Lim Twitter: @S_Alviere

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A bit of summary

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A bit of summary • Experiment on non-production codebases

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A bit of summary • Experiment on non-production codebases • Explore on the ﬁeld we know best

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A bit of summary • Experiment on non-production codebases • Explore on the ﬁeld we know best • Contribute back to community

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1500 70,000 BC UNIFICATION ANDROID DEVELOPER 4000 BC

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What should be a ﬁrst step?

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What should be a ﬁrst step?

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Why we start with companion app?

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Why we start with companion app? • Isolate from production code • Make us familiar android environment • Easier to evaluate new idea Image from github.com/artem-zinnatullin/qualitymatters

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What we found in build process?

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What we found in build process? • Build time

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What we found in build process? • Build time -> Not Signiﬁcant different

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What we found in build process? • Build time -> Not Signiﬁcant different • APK Size

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What we found in build process? • Build time -> Not Signiﬁcant different • APK Size -> ~400KB Added

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What we found in build process? • Build time -> Not Signiﬁcant different • APK Size -> ~400KB Added • Methods Count

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What we found in build process? • Build time -> Not Signiﬁcant different • APK Size -> ~400KB Added • Methods Count -> ~2k methods

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What about Tools?

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What about Tools? • Jacoco -> Coverage Report • Detekt -> Static Code Analysis

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Let’s start in production app

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Let’s start in production app

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We need a plan!! • Selected team starting to write a new feature with Kotlin.

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We need a plan!! • Knowledge Sharing for all the teams

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We need a plan!! • Deﬁne code style!!

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We need a plan!! • Channel to ask questions or suggestions

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After half a year…

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After half a year… • Everyone is writing Kotlin now.

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After half a year… • Everyone is writing Kotlin now. • We still sharing knowledge & Best practices among developers

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After half a year… • Everyone is writing Kotlin now. • We still sharing knowledge & Best practices among developers • Problems (e.g. code generation coverage)

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Code Generation Problems data class InstayFeedbackCategoryEntity( val id: Int, val title: String )

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Code Generation Problems public final class InstayFeedbackCategoryEntity { … public int hashCode() { return this.id * 31 + (this.title != null?this.title.hashCode():0); } public boolean equals(Object var1) { if(this != var1) { if(var1 instanceof InstayFeedbackCategoryEntity) { InstayFeedbackCategoryEntity var2 = (InstayFeedbackCategoryEntity)var1; if(this.id == var2.id && Intrinsics.areEqual(this.title, var2.title)) { return true; } } return false; } else { return true; } } }

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Solutions https://medium.com/@andrey.fomenkov/kotlin-jacoco-tuning-compiler-to-skip- generated-code-935fcaeaa391

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1900s 70,000 BC 4000 BC SCIENTIFIC REVOLUTION PART 4 1500s

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How we use Kotlin to make Android Development better?

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Data class

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@AutoValue public abstract class HotelDetailEntity { public abstract int hotelId(); public abstract String basicInformation(); public abstract List images(); public abstract List attractions(); public abstract List facilityIds(); public abstract List usefulInformation(); public abstract List reviews(); public static Builder builder() { return new AutoValue_HotelDetailEntity.Builder(); } @AutoValue.Builder public abstract static class Builder { public abstract HotelDetailEntity.Builder hotelId(int hotelId); public abstract HotelDetailEntity.Builder basicInformation(String basicInformation); public abstract HotelDetailEntity.Builder images(List images); public abstract HotelDetailEntity.Builder attractions(List attractionEntities); public abstract HotelDetailEntity.Builder facilityIds(List facilityIds); public abstract HotelDetailEntity.Builder usefulInformation(List usefulInformation); public abstract HotelDetailEntity.Builder reviews(List reviews); public abstract HotelUsefulInformationEntity build(); } }

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@AutoValue public abstract class HotelDetailEntity { public abstract int hotelId(); public abstract String basicInformation(); public abstract List images(); public abstract List attractions(); public abstract List facilityIds(); public abstract List usefulInformation(); public abstract List reviews(); public static Builder builder() { return new AutoValue_HotelDetailEntity.Builder(); } @AutoValue.Builder public abstract static class Builder { public abstract HotelDetailEntity.Builder hotelId(int hotelId); public abstract HotelDetailEntity.Builder basicInformation(String basicInformation); public abstract HotelDetailEntity.Builder images(List images); public abstract HotelDetailEntity.Builder attractions(List attractionEntities); public abstract HotelDetailEntity.Builder facilityIds(List facilityIds); public abstract HotelDetailEntity.Builder usefulInformation(List usefulInformation); public abstract HotelDetailEntity.Builder reviews(List reviews); public abstract HotelUsefulInformationEntity build(); } }

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data class HotelDetailEntity( val hotelId: Int, val basicInformation: BasicInformationEntity, val images: ImagesEntity, val attractions: List val facilityIds: List, val usefulInformation: List, val reviews: List )

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Custom View

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public class CheckInCheckOutDayTimeView extends LinearLayout { private TextView checkInLabel; private TextView checkOutLabel; public CheckInCheckOutDayTimeView(final Context context) { super(context); initView(); } public CheckInCheckOutDayTimeView(final Context context, @Nullable final AttributeSet attrs) { super(context, attrs); initView(); } public CheckInCheckOutDayTimeView(final Context context, @Nullable final AttributeSet attrs, final int defStyleAttr) { super(context, attrs, defStyleAttr); initView(); } @TargetApi(Build.VERSION_CODES.LOLLIPOP) public CheckInCheckOutDayTimeView(final Context context, @Nullable final AttributeSet attrs, final int defStyleAttr, final int defStyleRes) { super(context, attrs, defStyleAttr, defStyleRes); initView(); } private void initView() { View.inflate(getContext(), R.layout.layout_check_in_check_out_view, this); checkInLabel = findViewById(R.id.check_in_label); checkOutLabel = findViewById(R.id.check_out_label); } }

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public class CheckInCheckOutDayTimeView extends LinearLayout { private TextView checkInLabel; private TextView checkOutLabel; public CheckInCheckOutDayTimeView(final Context context) { super(context); initView(); } public CheckInCheckOutDayTimeView(final Context context, @Nullable final AttributeSet attrs) { super(context, attrs); initView(); } public CheckInCheckOutDayTimeView(final Context context, @Nullable final AttributeSet attrs, final int defStyleAttr) { super(context, attrs, defStyleAttr); initView(); } @TargetApi(Build.VERSION_CODES.LOLLIPOP) public CheckInCheckOutDayTimeView(final Context context, @Nullable final AttributeSet attrs, final int defStyleAttr, final int defStyleRes) { super(context, attrs, defStyleAttr, defStyleRes); initView(); } private void initView() { View.inflate(getContext(), R.layout.layout_check_in_check_out_view, this); checkInLabel = findViewById(R.id.check_in_label); checkOutLabel = findViewById(R.id.check_out_label); } }

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class CheckInCheckOutDayTimeView : LinearLayout { private val checkInLabel by lazy { findViewById(R.id.check_in_label) } private val checkOutLabel by lazy { findViewById(R.id.check_out_label) } @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0) : super(context, attrs, defStyleAttr) @TargetApi(Build.VERSION_CODES.LOLLIPOP) constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int, defStyleRes: Int) : super(context, attrs, defStyleAttr, defStyleRes) init { View.inflate(context, R.layout.layout_check_in_check_out_view, this) } }

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Collection Function

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public void setItems(final List items) { gridLayout.removeAllViews(); for (final String item : items) { if (!item.isEmpty()) { final TextView itemView = createItemView(item); gridLayout.addView(itemView); } } }

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public void setItems(final List items) { gridLayout.removeAllViews(); for (final String item : items) { if (!item.isEmpty()) { final TextView itemView = createItemView(item); gridLayout.addView(itemView); } } }

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fun setItems(texts: List) { gridLayout.removeAllViews() texts.asSequence() .filter(String::isNotEmpty) .map(::createItemView) .forEach(gridLayout::addView) }

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Safe Cast

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public class SimpleFragment extends Fragment { interface Listener { void showErrorDialog(final Throwable throwable); } public void onError(final Throwable throwable) { final Activity activity = getActivity(); if (activity instanceof Listener) { ((Listener) activity).showErrorDialog(throwable); } } }

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public class SimpleFragment extends Fragment { interface Listener { void showErrorDialog(final Throwable throwable); } public void onError(final Throwable throwable) { final Activity activity = getActivity(); if (activity instanceof Listener) { ((Listener) activity).showErrorDialog(throwable); } } }

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class SimpleFragment : Fragment() { interface Listener { fun showErrorDialog(throwable: Throwable) } fun onError(throwable: Throwable) { (activity as? Listener)?.showErrorDialog(throwable) } }

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Dagger

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@Inject lateinit var sneakerApi: SneakerApi @field:[Inject Named("layoutId")] @JvmField var layoutId: Int = 0

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@Module class DataModule { @Provides fun provideSneakerRepository(sneakerApi: SneakerApi) = SneakerRepositoryImpl(sneakerApi) }

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@Module class DataModule { @Provides fun provideSneakerRepository(sneakerApi: SneakerApi) = SneakerRepositoryImpl(sneakerApi) } @Module class DataModule { @Provides fun provideSneakerRepository(sneakerApi: SneakerApi): SneakerRepository = SneakerRepositoryImpl(sneakerApi) }

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Nullable from Java class

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@AutoValue public abstract class HotelDetailEntity { public abstract int hotelId(); public abstract String basicInformation(); public abstract List images(); public abstract List reviews(); }

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@AutoValue public abstract class HotelDetailEntity { public abstract int hotelId(); public abstract String basicInformation(); public abstract List images(); public abstract List reviews(); }

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@AutoValue public abstract class HotelDetailEntity { public abstract int hotelId(); @NotNull public abstract String basicInformation(); @NotNull public abstract List images(); @Nullable public abstract List reviews(); }

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Result • Development is easier, faster and more happy.

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Result • Development is easier, faster and more happy. • Goodbye Java :P

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Result • Development is easier, faster and more happy. • Goodbye Java :P • Kotlin forever !!

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HALL OF FAME https://github.com/agoda-com/fork https://github.com/VerachadW/kraph IVAN BALAKSHA VERACHAD W. BIRTH https://github.com/Judrummer/JxAdapter TIPATAI P. JU https://github.com/andreyfomenkov/kotlin ANDREI FOMENKOV

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ขอบคุณ THANK YOU! DESIGNED BY NETI SHEVAKIDAKARN