The document discusses Kotlin programming language features, including class syntax, constructors, properties, and lambda functions, complemented by code examples. It emphasizes the differences between Kotlin and Java, particularly in getters/setters and extension functions. Various programming patterns, like using optional lambdas and handling cursors, are also covered, illustrating how to effectively utilize Kotlin's capabilities.

1. Kotlin, why?
Pawel Byszewski
1

2. What is the talk
about?
Only necessary
Syntax
Code
patterns
Facts and
analysis

6. kotlin.com

7. kotlin.com

8. kotlin.com

9. kotlin.com

10. Syntax
10

11. class Conference(var name: String,
val startDate: Calendar,
val endDate: Calendar)
class Conference2(name: String,
val startDate: Calendar,
val endDate: Calendar) {
var name: String = name
get() = "prefix_$field"
set(value) {
field = "${value}_sufix"
}
}
Getters and setters

12. class Conference(var name: String,
val startDate: Calendar,
val endDate: Calendar)
class Conference2(name: String,
val startDate: Calendar,
val endDate: Calendar) {
var name: String = name
get() = "prefix_$field"
set(value) {
field = "${value}_sufix"
}
}
Getters and setters
val - finalvar - not final

13. class Conference(name: String,
val startDate: Calendar,
val endDate: Calendar) {
var name: String = name
}
Getters and setters
val - finalvar - not final

14. class Conference(name: String,
val startDate: Calendar,
val endDate: Calendar) {
var name: String = name
get() = "prefix_$field"
}
Getters and setters
“prefix” + field
val - finalvar - not final

15. class Conference(name: String,
val startDate: Calendar,
val endDate: Calendar) {
var name: String = name
get() = "prefix_$field"
}
Getters and setters
“prefix” + field
val - finalvar - not final
field - backing field
for property

16. class Conference(name: String,
val startDate: Calendar,
val endDate: Calendar) {
var name: String = name
get() = "prefix_$field"
set(value) {
field = "${value}_sufix"
}
}
Getters and setters
“prefix” + field
val - finalvar - not final
field - backing field
for property

17. Getters and setters
Lombok

18. Getters and setters
class Conference(val name: String,
val startDate: Calendar,
val endDate: Calendar) {
val passed: Boolean
get() = Calendar.getInstance().after(endDate)
}
It is property like in
C#, not java field

19. Getters and setters
class Conference(val name: String,
val startDate: Calendar,
val endDate: Calendar) {
val passed: Boolean
get() = Calendar.getInstance().after(endDate)
}
It doesn’t exist
It is property like in
C#, not java field

20. Constructor
class Conference(val name: String,
val city: String)
fun test() {
val conference = Conference("Confitura", "Warsaw")
}

21. Constructor
Lombok

22. Constructor
class Conference(val name: String,
val city: String,
val isFree: Boolean)
fun test() {
val conference = Conference("Confitura", "Warsaw")
}

23. Constructor
class Conference(val name: String,
val city: String,
val isFree: Boolean = false)
fun test() {
val conference = Conference("Confitura", "Warsaw")
}

24. public Conference(@NotNull String name,
@NotNull String city,
boolean isFree) {
Intrinsics.checkParameterIsNotNull(name, "name");
Intrinsics.checkParameterIsNotNull(city, "city");
this.name = name;
this.city = city;
this.isFree = isFree;
}
Constructor
One to rulethem all

25. public Conference(@NotNull String name,
@NotNull String city,
boolean isFree) {
Intrinsics.checkParameterIsNotNull(name, "name");
Intrinsics.checkParameterIsNotNull(city, "city");
this.name = name;
this.city = city;
this.isFree = isFree;
}
Constructor
val conference
= Conference("Confitura", "Warsaw")
One to rulethem all

26. public Conference(@NotNull String name,
@NotNull String city,
boolean isFree) {
Intrinsics.checkParameterIsNotNull(name, "name");
Intrinsics.checkParameterIsNotNull(city, "city");
this.name = name;
this.city = city;
this.isFree = isFree;
}
Constructor
public static final void test() {
Conference conference
= new Conference("Confitura", "Warsaw", false);
}
val conference
= Conference("Confitura", "Warsaw")
One to rulethem all

27. class Conference(val name: String,
val startDate: Calendar,
val endDate: Calendar)
fun test() {
val conference1 = Conference("Confitura",
Calendar.getInstance(),
Calendar.getInstance())
val conference2 = Conference(name = "Confitura",
startDate = Calendar.getInstance(),
endDate = Calendar.getInstance())
}
Constructor

28. class Conference(val name: String,
val startDate: Calendar,
val endDate: Calendar)
fun test() {
val conference1 = Conference("Confitura",
Calendar.getInstance(),
Calendar.getInstance())
val conference2 = Conference(name = "Confitura",
startDate = Calendar.getInstance(),
endDate = Calendar.getInstance())
}
Constructor
named arguments

29. Lambda
val function: () -> Unit
val function2: (String, Int) -> View
val function3: (String, Int) -> View = {name: String, count: Int -> doAction() }
val button: Button
button.setOnClickListener({ view: View -> doAction() })
button.setOnClickListener({ view -> doAction() })
button.setOnClickListener({ doAction() })
button.setOnClickListener {
doAction
}

30. Lambda
val function: () -> Unit
val function: (String, Int) -> View
val function3: (String, Int) -> View = {name: String, count: Int -> doAction() }
val button: Button
button.setOnClickListener({ view: View -> doAction() })
button.setOnClickListener({ view -> doAction() })
button.setOnClickListener({ doAction() })
button.setOnClickListener {
doAction
}

31. Lambda
val function: () -> Unit
val function: (String, Int) -> View
val function: (String, Int) -> View = {name: String, count: Int -> doAction() }
val button: Button
button.setOnClickListener({ view: View -> doAction() })
button.setOnClickListener({ view -> doAction() })
button.setOnClickListener({ doAction() })
button.setOnClickListener {
doAction
}
optional

32. Lambda
val function: () -> Unit
val function: (String, Int) -> View
val function: (String, Int) -> View = {name: String, count: Int -> doAction() }
val button: Button
button.setOnClickListener({ view: View -> doAction() })
button.setOnClickListener({ view -> doAction() })
button.setOnClickListener({ doAction() })
button.setOnClickListener {
doAction
}
optional

33. Lambda
val function: () -> Unit
val function: (String, Int) -> View
val function: (String, Int) -> View = {name: String, count: Int -> doAction() }
val button: Button
button.setOnClickListener({ view: View -> doAction() })
button.setOnClickListener({ view -> doAction() })
button.setOnClickListener({ doAction() })
button.setOnClickListener {
doAction
}
optional

34. Lambda
val function: () -> Unit
val function: (String, Int) -> View
val function: (String, Int) -> View = {name: String, count: Int -> doAction() }
val button: Button
button.setOnClickListener({ view: View -> doAction() })
button.setOnClickListener({ view -> doAction() })
button.setOnClickListener({ doAction() })
button.setOnClickListener {
doAction
}
optional

35. Lambda
val function: () -> Unit
val function: (String, Int) -> View
val function: (String, Int) -> View = {name: String, count: Int -> doAction() }
val button: Button
button.setOnClickListener({ view: View -> doAction() })
button.setOnClickListener({ view -> doAction() })
button.setOnClickListener({ doAction() })
button.setOnClickListener {
doAction
}
optional

36. Lambda
val function: () -> Unit
val function: (String, Int) -> View
val function: (String, Int) -> View = {name: String, count: Int -> doAction() }
val button: Button
button.setOnClickListener({ view: View -> doAction() })
button.setOnClickListener({ view -> doAction() })
button.setOnClickListener({ doAction() })
button.setOnClickListener {
doAction()
}
optional

37. Lambda
Retrolambda
Java8

38. Lambda
fun test() {
println("one")
println("two")
println("three")
}

39. Lambda
fun test() {
performAction {
println("two")
}
}
fun performAction(action: () -> Unit) {
println("one")
action()
println("three")
}
fun test() {
println("one")
println("two")
println("three")
}

40. Lambda
fun test() {
performAction {
println("two")
}
}
fun performAction(action: () -> Unit) {
println("one")
action()
println("three")
}
public final class LabmdaSample {
public final void test() {
this.performAction((Function0)test.INSTANCE);
}
}

41. Lambda
fun test() {
performAction {
println("two")
}
}
public final class LabmdaSample {
public final void test() {
this.performAction((Function0)test.INSTANCE);
}
}
public final void performAction(@NotNull Function0<Unit> action) {
Intrinsics.checkParameterIsNotNull(action, (String)"action");
String message$iv = "one";
System.out.println((Object)message$iv);
action.invoke();
message$iv = "three";
System.out.println((Object)message$iv);
}
fun performAction(action: () -> Unit) {
println("one")
action()
println("three")
}

42. Lambda
fun test() {
performAction {
println("two")
}
}
public final class LabmdaSample {
public final void test() {
this.performAction((Function0)test.INSTANCE);
}
}
public final void performAction(@NotNull Function0<Unit> action) {
Intrinsics.checkParameterIsNotNull(action, (String)"action");
String message$iv = "one";
System.out.println((Object)message$iv);
action.invoke();
message$iv = "three";
System.out.println((Object)message$iv);
}
fun performAction(action: () -> Unit) {
println("one")
action()
println("three")
}

43. Lambda
public final class LabmdaSample {
public final void test() {
this.performAction((Function0)test.INSTANCE);
}
}
public final void performAction(@NotNull Function0<Unit> action) {
Intrinsics.checkParameterIsNotNull(action, (String)"action");
String message$iv = "one";
System.out.println((Object)message$iv);
action.invoke();
message$iv = "three";
System.out.println((Object)message$iv);
}
static final class LabmdaSample.test
extends Lambda
implements Function0<Unit> {
public static final LabmdaSample.test
INSTANCE = new test();
public final void invoke() {
String message$iv = "two";
System.out.println((Object)message$iv);
}
LabmdaSample.test() {
super(0);
}
}

44. Lambda
fun test() {
performAction {
println("two")
}
}
inline fun performAction(
noinline action: () -> Unit) {
println("one")
action()
println("three")
}

45. public final void test() {
LabmdaSample labmdaSample = this;
Function0 action$iv = test.INSTANCE;
String message$iv$iv = "one";
System.out.println((Object)message$iv$iv);
action$iv.invoke();
message$iv$iv = "three";
System.out.println((Object)message$iv$iv);
}
Lambda
fun test() {
performAction {
println("two")
}
}
inline fun performAction(
noinline action: () -> Unit) {
println("one")
action()
println("three")
}
disappeared

46. Lambda
fun test() {
performAction {
println("two")
}
}
inline fun performAction(
action: () -> Unit) {
println("one")
action()
println("three")
}
Let the magic begin

47. public final void test() {
LabmdaSample this_$iv = this;
String message$iv$iv = "one";
System.out.println((Object)message$iv$iv);
String message$iv = "two";
System.out.println((Object)message$iv);
message$iv$iv = "three";
System.out.println((Object)message$iv$iv);
}
Lambda
fun test() {
performAction {
println("two")
}
}
inline fun performAction(
action: () -> Unit) {
println("one")
action()
println("three")
}
disappeared

48. class Person(val name: String, val age: Int)
fun Person.isUnderAge()
= age < 18
Extension functions

49. class Person(val name: String, val age: Int)
fun Person.isUnderAge()
= age < 18
fun test() {
val person = Person("Pawel", 18)
person.isUnderAge()
}
Extension functions
Mixins are a language concept that allows
a programmer to inject some code into a class

50. class Person(val name: String, val age: Int)
fun Person.isUnderAge()
= age < 18
fun test() {
val person = Person("Pawel", 18)
person.isUnderAge()
}
Extension functions
but, it isn’t mixin
Mixins are a language concept that allows
a programmer to inject some code into a class

51. public final class Person {
@NotNull
private final String name;
private final int age;
@NotNull
public final String getName() {
return this.name;
}
public final int getAge() {
return this.age;
}
public Person(@NotNull String name, int age) {
Intrinsics.checkParameterIsNotNull((Object)name,
(String)"name");
this.name = name;
this.age = age;
}
}
Extension functions
public final class TestExtensionKt {
public static final boolean isUnderAge(
Person $receiver){
Intrinsics.checkParameterIsNotNull((Object)$receiver,
(String)"$receiver");
return $receiver.getAge() < 18;
}
public static final void test() {
Person person = new Person("Pawel", 18);
}
}
Just like Utils

52. Patterns and
constructions
52

53. Extensions != utils
53

54. fun readFromCursor(cursor: Cursor, name: String): String? {
val columnIndex = cursor.getColumnIndex(name)
return if (cursor.isNull(columnIndex)) {
null
} else {
cursor.getString(columnIndex)
}
}
fun show(cursor: Cursor) {
try {
showName(readFromCursor(cursor, "name"))
showAge(readFromCursor(cursor, "age"))
} finally {
cursor.close()
}
}
Extensions != utils
id name age
0 Pawel 30
1 Kasia 25
... ... ...

55. fun readFromCursor(cursor: Cursor, name: String): String? {
val columnIndex = cursor.getColumnIndex(name)
return if (cursor.isNull(columnIndex)) {
null
} else {
cursor.getString(columnIndex)
}
}
fun show(cursor: Cursor) {
try {
showName(readFromCursor(cursor, "name"))
showAge(readFromCursor(cursor, "age"))
} finally {
cursor.close()
}
}
Extensions != utils
id name age
0 Pawel 30
1 Kasia 25
... ... ... android

56. fun readFromCursor(cursor: Cursor, name: String): String? {
val columnIndex = cursor.getColumnIndex(name)
return if (cursor.isNull(columnIndex)) {
null
} else {
cursor.getString(columnIndex)
}
}
fun show(cursor: Cursor) {
try {
showName(readFromCursor(cursor, "name"))
showAge(readFromCursor(cursor, "age"))
} finally {
cursor.close()
}
}
Extensions != utils
id name age
0 Pawel 30
1 Kasia 25
... ... ...

57. Extensions != utils
fun Cursor.readString(name: String): String? {
val columnIndex = getColumnIndex(name)
return if (isNull(columnIndex)) {
null
} else {
getString(columnIndex)
}
}
fun show(cursor: Cursor) {
try {
showName(readFromCursor(cursor, "name"))
showAge(readFromCursor(cursor, "age"))
} finally {
cursor.close()
}
}
id name age
0 Pawel 30
1 Kasia 25
... ... ...

58. Extensions != utils
fun Cursor.readString(name: String): String? {
val columnIndex = getColumnIndex(name)
return if (isNull(columnIndex)) {
null
} else {
getString(columnIndex)
}
}
fun show(cursor: Cursor) {
try {
showName(cursor.readString("name"))
showAge(cursor.readString("age"))
} finally {
cursor.close()
}
}
id name age
0 Pawel 30
1 Kasia 25
... ... ...

59. fun Cursor.closeAfter(action: () -> Unit) {
try {
action()
} finally {
close()
}
}
Extensions != utils
fun Cursor.readString(name: String): String? {
val columnIndex = getColumnIndex(name)
return if (isNull(columnIndex)) {
null
} else {
getString(columnIndex)
}
}
fun show(cursor: Cursor) {
try {
showName(cursor.readString("name"))
showAge(cursor.readString("age"))
} finally {
cursor.close()
}
}

60. Extensions != utils
fun Cursor.readString(name: String): String? {
val columnIndex = getColumnIndex(name)
return if (isNull(columnIndex)) {
null
} else {
getString(columnIndex)
}
}
fun show(cursor: Cursor) {
cursor.closeAfter {
showName(cursor.readString("name"))
showAge(cursor.readString("age"))
}
}
fun Cursor.closeAfter(action: () -> Unit) {
try {
action()
} finally {
close()
}
}

61. Extensions != utils
fun Cursor.readString(name: String): String? {
val columnIndex = getColumnIndex(name)
return if (isNull(columnIndex)) {
null
} else {
getString(columnIndex)
}
}
fun show(cursor: Cursor) {
cursor.closeAfter {
showName(cursor.readString("name"))
showAge(cursor.readString("age"))
}
}
fun Cursor.closeAfter(action: (Cursor) -> Unit) {
try {
action(this)
} finally {
close()
}
}

62. Extensions != utils
fun Cursor.readString(name: String): String? {
val columnIndex = getColumnIndex(name)
return if (isNull(columnIndex)) {
null
} else {
getString(columnIndex)
}
}
fun show(cursor: Cursor) {
cursor.closeAfter {
showName(it.readString("name"))
showName(it.readString("age"))
}
}
fun Cursor.closeAfter(action: (Cursor) -> Unit) {
try {
action(this)
} finally {
close()
}
}
it: Cursor

63. Extensions != utils
fun Cursor.readString(name: String): String? {
val columnIndex = getColumnIndex(name)
return if (isNull(columnIndex)) {
null
} else {
getString(columnIndex)
}
}
fun show(cursor: Cursor) {
cursor.closeAfter {
showName(it.readString("name"))
showName(it.readString("age"))
}
}
fun Cursor.closeAfter(action: Cursor.() -> Unit) {
try {
action()
} finally {
close()
}
}

64. Extensions != utils
fun Cursor.readString(name: String): String? {
val columnIndex = getColumnIndex(name)
return if (isNull(columnIndex)) {
null
} else {
getString(columnIndex)
}
}
fun show(cursor: Cursor) {
cursor.closeAfter {
showName(readString("name"))
showName(readString("age"))
}
}
fun Cursor.closeAfter(action: Cursor.() -> Unit) {
try {
action()
} finally {
close()
}
} this === cursor
(this as Cursor).action()

65. Extensions != utils
fun Cursor.readString(name: String): String? {
val columnIndex = getColumnIndex(name)
return if (isNull(columnIndex)) {
null
} else {
getString(columnIndex)
}
}
public static final void show(@NotNull Cursor cursor) {
Intrinsics.checkParameterIsNotNull((Object)cursor,(String)"cursor");
CursorReadyKt.closeAfter(cursor,
(Function1)show.INSTANCE);
}
fun Cursor.closeAfter(action: Cursor.() -> Unit) {
try {
action()
} finally {
close()
}
}

66. Extensions != utils
public static final void closeAfter(
Cursor $receiver,
@NotNull Function1<? super Cursor, Unit> action) {
Intrinsics.checkParameterIsNotNull((Object)$receiver, (String)"$receiver");
Intrinsics.checkParameterIsNotNull(action,(String)"action");
try {
action.invoke((Object)$receiver);
} finally {
$receiver.close();
}
}
fun Cursor.readString(name: String): String? {
val columnIndex = getColumnIndex(name)
return if (isNull(columnIndex)) {
null
} else {
getString(columnIndex)
}
}
public static final void show(@NotNull Cursor cursor) {
Intrinsics.checkParameterIsNotNull((Object)cursor,(String)"cursor");
CursorReadyKt.closeAfter(cursor,
(Function1)show.INSTANCE);
}

67. Extensions != utils
static final class CursorReadyKt.show
extends Lambda
implements Function1<Cursor, Unit> {
public static final CursorReadyKt.show INSTANCE = new ;
public final void invoke(Cursor $receiver) {
Intrinsics.checkParameterIsNotNull((Object)$receiver, (String)"$receiver");
CursorSampleKt.showName((String)CursorSampleKt.readString(
(Cursor)$receiver,
(String)"name")
);
CursorSampleKt.showName((String)CursorSampleKt.readString(
(Cursor)$receiver,
(String)"age")
);
}
}
public static final void closeAfter(
Cursor $receiver,
@NotNull Function1<? super Cursor, Unit> action) {
Intrinsics.checkParameterIsNotNull((Object)$receiver, (String)"$receiver");
Intrinsics.checkParameterIsNotNull(action,(String)"action");
try {
action.invoke((Object)$receiver);
} finally {
$receiver.close();
}
}

68. Extensions != utils
fun Cursor.readString(name: String): String? {
val columnIndex = getColumnIndex(name)
return if (isNull(columnIndex)) {
null
} else {
getString(columnIndex)
}
}
fun show(cursor: Cursor) {
cursor.closeAfter {
showName(readString("name"))
showName(readString("age"))
}
}
inline fun Cursor.closeAfter(
action: Cursor.() -> Unit) {
try {
action()
} finally {
close()
}
}
this === cursor
(this as Cursor).action()

69. Extensions != utils
fun show(cursor: Cursor) {
cursor.closeAfter {
showName(readString("name"))
showName(readString("age"))
}
}
inline fun Cursor.closeAfter(
action: Cursor.() -> Unit) {
try {
action()
} finally {
close()
}
}

70. Extensions != utils
public static final void show(@NotNull Cursor cursor) {
Intrinsics.checkParameterIsNotNull(cursor, "cursor");
try {
Cursor $receiver = cursor;
CursorSampleKt.showName(
CursorSampleKt.readString($receiver, "name"));
CursorSampleKt.showName(
CursorSampleKt.readString($receiver, "age"));
Unit unit = Unit.INSTANCE;
} finally {
cursor.close();
}
}
}
fun show(cursor: Cursor) {
cursor.closeAfter {
showName(readString("name"))
showName(readString("age"))
}
}
inline fun Cursor.closeAfter(
action: Cursor.() -> Unit) {
try {
action()
} finally {
close()
}
}
disappeared

71. Delegated properties
71

72. class Example {
var p: String by Delegate()
}
class Delegate {
operator fun getValue(thisRef: Any?, property: KProperty<*>): String {
return "example"
}
operator fun setValue(thisRef: Any?, property: KProperty<*>, value: String) {
}
}
Delegated properties
Controls access to the field

73. class SampleActivity : AppCompatActivity {
lateinit val inputMethodManager: InputMethodManager
override fun onCreate(savedInstanceState: Bundle?) {
inputManager: InputMethodManager = getSystemService(Activity.INPUT_METHOD_SERVICE)
as InputMethodManager
}
}
class SampleActivity : AppCompatActivity {
val inputManager: InputMethodManager
by bindSystemService(Activity.INPUT_METHOD_SERVICE)
override fun onCreate(savedInstanceState: Bundle?) {
}
}
Delegated properties

74. class SampleActivity : AppCompatActivity {
lateinit val inputMethodManager: InputMethodManager
override fun onCreate(savedInstanceState: Bundle?) {
inputManager: InputMethodManager = getSystemService(Activity.INPUT_METHOD_SERVICE)
as InputMethodManager
}
}
class SampleActivity : AppCompatActivity {
val inputManager: InputMethodManager
by bindSystemService(Activity.INPUT_METHOD_SERVICE)
override fun onCreate(savedInstanceState: Bundle?) {
}
}
Delegated properties

75. public interface ReadOnlyProperty<in R, out T> {
public operator fun getValue(thisRef: R, property: KProperty<*>): T
}
class Lazy<T, V>(private val initializer: (T, KProperty<*>) -> V) : ReadOnlyProperty<T, V> {
private object EMPTY
private var value: Any? = EMPTY
override fun getValue(thisRef: T, property: KProperty<*>): V {
if (value == EMPTY) {
value = initializer(thisRef, property)
}
@Suppress("UNCHECKED_CAST")
return value as V
}
}
Delegated properties
Helps to remember about syntax
Calls given factory lazy

76. fun <V> Activity.bindSystemService(serviceName: String)
: ReadOnlyProperty<Activity, V> = Lazy { activity: Activity, property: KProperty<*> ->
activity.getSystemServicce(serviceName) as V?
?: systemServiceNotFound(serviceName, property)
}
Delegated properties
Helper interface Lazy factory caller

77. fun <V> Activity.bindSystemService(serviceName: String)
: ReadOnlyProperty<Activity, V> = Lazy { activity: Activity, property: KProperty<*> ->
activity.getSystemServicce(serviceName) as V?
?: systemServiceNotFound(serviceName, property)
}
fun <V> Activity.bindSystemService(serviceName: String)
: ReadOnlyProperty<Activity, V> = fetchSystemService(serviceName, Activity::getSystemService)
@Suppress("UNCHECKED_CAST")
inline fun <V> fetchSystemService(serviceName: String,
crossinline serviceBinder: Activity.(String) -> Any)
= Lazy { t: Activity, property: KProperty<*> ->
t.serviceBinder(serviceName) as V? ?: systemServiceNotFound(serviceName, property)
}
Delegated properties
Helper interface Lazy factory caller
Extract service !!

78. fun <V> Activity.bindSystemService(serviceName: String)
: ReadOnlyProperty<Activity, V> = fetchSystemService(serviceName, Activity::getSystemService)
@Suppress("UNCHECKED_CAST")
inline fun <V> fetchSystemService(serviceName: String, crossinline serviceBinder: Activity.(String) -> Any)
= Lazy { t: Activity, property: KProperty<*> ->
t.serviceBinder(serviceName) as V? ?: systemServiceNotFound(serviceName, property)
}
Delegated properties

79. fun <V> Activity.bindSystemService(serviceName: String)
: ReadOnlyProperty<Activity, V> = fetchSystemService(serviceName, Activity::getSystemService)
fun <V> Fragment.bindSystemService(serviceName: String)
: ReadOnlyProperty<Fragment, V> = fetchSystemService(serviceName, Fragment::serviceBinder)
@Suppress("UNCHECKED_CAST")
inline fun <V> fetchSystemService(serviceName: String, crossinline serviceBinder: Activity.(String) -> Any)
= Lazy { t: Activity, property: KProperty<*> ->
t.serviceBinder(serviceName) as V? ?: systemServiceNotFound(serviceName, property)
}
Delegated properties

80. fun <V> Activity.bindSystemService(serviceName: String)
: ReadOnlyProperty<Activity, V> = fetchSystemService(serviceName, Activity::getSystemService)
fun <V> Fragment.bindSystemService(serviceName: String)
: ReadOnlyProperty<Fragment, V> = fetchSystemService(serviceName, Fragment::serviceBinder)
@Suppress("UNCHECKED_CAST")
inline fun <V> fetchSystemService(serviceName: String, crossinline serviceBinder: Activity.(String) -> Any)
= Lazy { t: Activity, property: KProperty<*> ->
t.serviceBinder(serviceName) as V? ?: systemServiceNotFound(serviceName, property)
}
@Suppress("UNCHECKED_CAST")
inline fun <T, V> fetchSystemService(serviceName: String, crossinline serviceBinder: T.(String) -> Any)
= Lazy { t: T, property: KProperty<*> ->
t.serviceBinder(serviceName) as V? ?: systemServiceNotFound(serviceName, property)
}
Delegated properties

81. fun <V> Activity.bindSystemService(serviceName: String)
: ReadOnlyProperty<Activity, V> = fetchSystemService(serviceName, Activity::getSystemService)
fun <V> Fragment.bindSystemService(serviceName: String)
: ReadOnlyProperty<Fragment, V> = fetchSystemService(serviceName, Fragment::serviceBinder)
@Suppress("UNCHECKED_CAST")
inline fun <V> fetchSystemService(serviceName: String, crossinline serviceBinder: Activity.(String) -> Any)
= Lazy { t: Activity, property: KProperty<*> ->
t.serviceBinder(serviceName) as V? ?: systemServiceNotFound(serviceName, property)
}
@Suppress("UNCHECKED_CAST")
inline fun <T, V> fetchSystemService(serviceName: String, crossinline serviceBinder: T.(String) -> Any)
= Lazy { t: T, property: KProperty<*> ->
t.serviceBinder(serviceName) as V? ?: systemServiceNotFound(serviceName, property)
}
Delegated properties

82. Facts
82

83. Size
Methods Dex size (KB)
kotlin-stdlib 6961 1085
kotlin-runtime 924 149
7885 1234

84. Compilation
BUILD SUCCESSFUL
Total time: 1 mins 45.011 secs
== Build Time Summary ==
:app:clean (0:00.667) ▇ 1%
:app:prepareAndroidBrasterLibraryUnspecifiedLibrary (0:00.926) ▇▇ 1%
:app:prepareComAndroidSupportAppcompatV72330Library (0:00.345) 0%
:app:prepareIoRealmRealmAndroidLibrary100Library (0:00.151) 0%
:app:mergeDebugAssets (0:00.058) 0%
:app:processDebugManifest (0:00.200) 0%
:app:fabricGenerateResourcesDebug (0:00.119) 0%
:app:mergeDebugResources (0:09.250) ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 9%
:app:dataBindingProcessLayoutsDebug (0:00.695) ▇ 1%
:app:generateDebugSettings (0:00.139) 0%
:app:processDebugResources (0:00.668) ▇ 1%
:app:compileDebugKotlin (0:13.807) ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 14%
:app:compileDebugJavaWithJavac (0:04.937) ▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 5%
:app:compileDebugGroovyWithGroovyc (0:03.566) ▇▇▇▇▇▇▇▇▇▇ 4%
:app:compileDebugKotlinAfterJava (0:11.675) ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 12%
:app:transformClassesWithRealmTransformerForDebug (0:01.685) ▇▇▇▇ 2%
:app:transformClassesWithDexForDebug (0:37.963)<-- ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 39%
:app:transformNative_libsWithMergeJniLibsForDebug (0:00.516) ▇ 1%
:app:transformResourcesWithMergeJavaResForDebug (0:00.204) 0%
:app:packageDebug (0:09.790) ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 10%
:app:zipalignDebug (0:00.315) 0%
== BUILD SUCCESSFUL ==

85. Compilation
BUILD SUCCESSFUL
Total time: 1 mins 45.011 secs
== Build Time Summary ==
:app:clean (0:00.667) ▇ 1%
:app:prepareAndroidBrasterLibraryUnspecifiedLibrary (0:00.926) ▇▇ 1%
:app:prepareComAndroidSupportAppcompatV72330Library (0:00.345) 0%
:app:prepareIoRealmRealmAndroidLibrary100Library (0:00.151) 0%
:app:mergeDebugAssets (0:00.058) 0%
:app:processDebugManifest (0:00.200) 0%
:app:fabricGenerateResourcesDebug (0:00.119) 0%
:app:mergeDebugResources (0:09.250) ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 9%
:app:dataBindingProcessLayoutsDebug (0:00.695) ▇ 1%
:app:generateDebugSettings (0:00.139) 0%
:app:processDebugResources (0:00.668) ▇ 1%
:app:compileDebugKotlin (0:13.807) ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 14%
:app:compileDebugJavaWithJavac (0:04.937) ▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 5%
:app:compileDebugGroovyWithGroovyc (0:03.566) ▇▇▇▇▇▇▇▇▇▇ 4%
:app:compileDebugKotlinAfterJava (0:11.675) ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 12%
:app:transformClassesWithRealmTransformerForDebug (0:01.685) ▇▇▇▇ 2%
:app:transformClassesWithDexForDebug (0:37.963)<-- ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 39%
:app:transformNative_libsWithMergeJniLibsForDebug (0:00.516) ▇ 1%
:app:transformResourcesWithMergeJavaResForDebug (0:00.204) 0%
:app:packageDebug (0:09.790) ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 10%
:app:zipalignDebug (0:00.315) 0%
== BUILD SUCCESSFUL ==
26%

86. What next?
Kotlin 1.0.x which will be a series of releases containing bug fixes, updates to tooling, IDE support and other areas which do not affect the core language.
1.0.x releases will be published on a regular basis once every several weeks.
Kotlin 1.1 which will contain major new language features, along with all the improvements from the 1.0.x branch. This will be a feature-driven
release, and we aren’t announcing any specific time frame for it.
async/await/yield
Type aliases
Local delegated properties
Java 8/9 Support
Jack and Jill toolchain
Instant Run

87. Summary
Syntax
Inline
Java

88. 88
Pawel Byszewski
pawel.byszewski@polidea.com
pawell.b@gmail.com
https://twitter.com/PawelByszewski

89. 89
Pawel Byszewski
THANK
YOU
http://www.meetup.com/Mobile-Warsaw/

90. FGST
Free GoogleSlides
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