A presentation at KotlinConf in in San Francisco, CA, USA by Jake Wharton
Kotlin Code Generation Alec Strong & Jake Wharton
public final class User {
private final String firstName ; private final String lastName ; private final int age ; public User (String firstName , String lastName , int age) {
this . firstName = firstName ; this . lastName = lastName ; this . age = age ;
}
public String getFirstName () {
return firstName ;
}
public String getLastName () {
return lastName ;
}
public int getAge () {
return age ;
}
@Override public boolean equals (Object o) {
if ( this == o) return true; if (o == null || getClass() != o.getClass()) return false;
User user = (User) o ; return age == user. age
&& Objects. equals ( firstName , user. firstName ) && Objects. equals ( lastName , user. lastName ) ;
}
@Override public int hashCode () {
return Objects. hash ( firstName , lastName , age ) ;
}
@Override public String toString () {
return "User{"
"firstName='"
firstName
' ' '
", lastName='"
lastName
' ' '
", age="
age
'}' ;
} } data class User(
val firstName : String , val lastName : String , val age : Int )
Bytecode
Protocol Buffers
Protocol Buffers SQL
Protocol Buffers SQL Swagger
Protocol Buffers SQL Swagger Android XML
Protocol Buffers SQL Swagger Android XML YAML
Protocol Buffers SQL Swagger Android XML YAML Mirrors/Elements
SQL Swagger Android XML YAML Mirrors/Elements PSI
Swagger Android XML YAML Mirrors/Elements PSI UAST
Android XML YAML Mirrors/Elements PSI UAST
???
Protocol Buffers
SQL
Swagger
Android XML
YAML
Mirrors/Elements
PSI
UAST
???
Protocol Buffers
syntax = "proto2" ; package com.sample; message Ogre {
required string name = 1 ;
repeated int32 layers = 2 ;
optional string swamp = 3 ; }
public final String name ; public final List<Integer> layers ;
public final String swamp ; public Ogre (String name , List<Integer> layers , String swamp) {
this (name , layers , swamp , ByteString. EMPTY ) ; } public Ogre (String name , List<Integer> layers , String swamp ,
ByteString unknownFields) {
super ( ADAPTER , unknownFields) ; this . name = name ; this . layers = Internal. immutableCopyOf ( "layers" , layers) ; this . swamp = swamp ; }
public final String name ; public final List<Integer> layers ;
public final String swamp ; public Ogre (String name , List<Integer> layers , String swamp) {
this (name , layers , swamp , ByteString. EMPTY ) ; } public Ogre (String name , List<Integer> layers , String swamp ,
ByteString unknownFields) {
super ( ADAPTER , unknownFields) ; this . name = name ; this . layers = Internal. immutableCopyOf ( "layers" , layers) ; this . swamp = swamp ; } public final String name ; public final List<Integer> layers ;
public final String swamp ; this . name = name ; this . layers = Internal. immutableCopyOf ( "layers" , layers) ; this . swamp = swamp ;
public final String name ; public final List<Integer> layers ;
public final String swamp ; public Ogre (String name , List<Integer> layers , String swamp) {
this (name , layers , swamp , ByteString. EMPTY ) ; } public Ogre (String name , List<Integer> layers , String swamp ,
ByteString unknownFields) {
super ( ADAPTER , unknownFields) ; this . name = name ; this . layers = Internal. immutableCopyOf ( "layers" , layers) ; this . swamp = swamp ; }
ByteString. EMPTY
ByteString unknownFields
public final String name ; public final List<Integer> layers ;
public final String swamp ; public Ogre (String name , List<Integer> layers , String swamp) {
this (name , layers , swamp , ByteString. EMPTY ) ; } public Ogre (String name , List<Integer> layers , String swamp ,
ByteString unknownFields) {
super ( ADAPTER , unknownFields) ; this . name = name ; this . layers = Internal. immutableCopyOf ( "layers" , layers) ; this . swamp = swamp ; }
Internal. immutableCopyOf ( "layers" , layers)
public final String name ; public final List<Integer> layers ;
public final String swamp ; public Ogre (String name , List<Integer> layers , String swamp) {
this (name , layers , swamp , ByteString. EMPTY ) ; } public Ogre (String name , List<Integer> layers , String swamp ,
ByteString unknownFields) {
super ( ADAPTER , unknownFields) ; this . name = name ; this . layers = Internal. immutableCopyOf ( "layers" , layers) ; this . swamp = swamp ; }
String name
String swamp
String name
String swamp
String name
String swamp
public final String name ; public final List<Integer> layers ;
public final String swamp ; public Ogre (String name , List<Integer> layers , String swamp) {
this (name , layers , swamp , ByteString. EMPTY ) ; } public Ogre (String name , List<Integer> layers , String swamp ,
ByteString unknownFields) {
super ( ADAPTER , unknownFields) ; this . name = name ; this . layers = Internal. immutableCopyOf ( "layers" , layers) ; this . swamp = swamp ; }
class Ogre @JvmOverloads constructor (
val name : String , val layers : List<Int> , val swamp : String? ,
unknownFields: ByteString = ByteString. EMPTY ) : Message<Ogre , Ogre.Builder>( ADAPTER , unknownFields)
class Ogre @JvmOverloads constructor (
val name : String , val layers : List<Int> , val swamp : String? ,
unknownFields: ByteString = ByteString. EMPTY ) : Message<Ogre , Ogre.Builder>( ADAPTER , unknownFields)
val name : String , val layers : List<Int> , val swamp : String? , Ogre shrek = new Ogre( "Shrek" , Arrays. asList ( 1 , 2 ) , null ) ;
System. out .println(shrek.getSwamp()) ;
s
class Ogre @JvmOverloads constructor (
@JvmField val name : String , @JvmField val layers : List<Int> , @JvmField val swamp : String? ,
unknownFields: ByteString = ByteString. EMPTY ) : Message<Ogre , Ogre.Builder>( ADAPTER , unknownFields)
@JvmField val name : String , @JvmField val layers : List<Int> , @JvmField val swamp : String? , Ogre shrek = new Ogre( "Shrek" , Arrays. asList ( 1 , 2 ) , null ) ;
System. out .println(shrek. swamp ) ;
S e
override fun equals (other: Any?): Boolean {
if (other === this ) return true if (other !is OgreKt) return false val o = other as OgreKt?
return (unknownFields() == o!!.unknownFields() && name == o. name
&& layers == o. layers
&& Internal.equals( swamp , o. swamp )) } override fun hashCode (): Int {
var result = super . hashCode
if (result == 0 ) { result = unknownFields().hashCode() result = result * 37 + name .hashCode() result = result * 37 + layers .hashCode() result = result * 37
super . hashCode = result }
return result } override fun toString (): String {
val builder = StringBuilder() builder.append( ", name=" ).append( name )
if (! layers .isEmpty()) builder.append( ", layers=" ).append( layers )
if ( swamp != null ) builder.append( ", swamp=" ).append( swamp )
return builder.replace( 0 , 2 , "Ogre{" ).append( '}' ).toString() }
class Ogre @JvmOverloads constructor (
@JvmField val name : String , @JvmField val layers : List<Int> , @JvmField val swamp : String? ,
unknownFields: ByteString = ByteString. EMPTY ) : Message<Ogre , Ogre.Builder>( ADAPTER , unknownFields)
data class Ogre @JvmOverloads constructor (
@JvmField val name : String , @JvmField val layers : List<Int> , @JvmField val swamp : String? ,
unknownFields: ByteString = ByteString. EMPTY ) : Message<Ogre , Ogre.Builder>( ADAPTER , unknownFields)
data class Ogre @JvmOverloads constructor (
@JvmField val name : String , @JvmField val layers : List<Int> , @JvmField val swamp : String? ,
unknownFields: ByteString = ByteString. EMPTY ) : Message<Ogre , Ogre.Builder>( ADAPTER , unknownFields) data class Ogre
unknownFields: ByteString = ByteString.EMPTY
data class Ogre @JvmOverloads constructor (
@JvmField val name : String , @JvmField val layers : List<Int> , @JvmField val swamp : String? , private val unknownFields: ByteString = ByteString. EMPTY ) : Message<Ogre , Ogre.Builder>( ADAPTER , unknownFields) data class Ogre
private val
unknownFields : ByteString = ByteString. EMPTY
class Ogre @JvmOverloads constructor (
@JvmField val name : String , @JvmField val layers : List<Int> , @JvmField val swamp : String? ,
unknownFields: ByteString = ByteString. EMPTY ) : Message<Ogre , Ogre.Builder>( ADAPTER , unknownFields)
public static final class Builder extends Message.Builder<Ogre , Builder> {
public String name ; public List<Integer> layers ; public String swamp ; public Builder () {
layers = Internal. newMutableList () ;
}
public Builder name (String name) {
this . name = name ; return this;
}
public Builder layers (List<Integer> layers) { Internal. checkElementsNotNull (layers) ; this . layers = layers ; return this;
}
public Builder swamp (String swamp) {
this . swamp = swamp ; return this;
}
@Override public
Ogre build () {
null ) {
throw Internal. missingRequiredFields ( name , "name" ) ;
}
return new Ogre( name , layers , swamp , super .buildUnknownFields()) ;
} }
public static final class Builder extends Message.Builder<Ogre , Builder> {
public String name ; public List<Integer> layers ; public String swamp ; public Builder () {
layers = Internal. newMutableList () ;
}
public Builder name (String name) {
this . name = name ; return this;
}
public Builder layers (List<Integer> layers) { Internal. checkElementsNotNull (layers) ; this . layers = layers ; return this;
}
public Builder swamp (String swamp) {
this . swamp = swamp ; return this;
}
@Override public
Ogre build () {
null ) {
throw Internal. missingRequiredFields ( name , "name" ) ;
}
return new Ogre( name , layers , swamp , super .buildUnknownFields()) ;
} } Internal. checkElementsNotNull (layers) ;
null ) {
throw Internal. missingRequiredFields ( name , "name" ) ;
}
public static final class Builder extends Message.Builder<Ogre , Builder> {
public String name ; public List<Integer> layers ; public String swamp ; public Builder () {
layers = Internal. newMutableList () ;
}
public Builder name (String name) {
this . name = name ; return this;
}
public Builder layers (List<Integer> layers) { Internal. checkElementsNotNull (layers) ; this . layers = layers ; return this;
}
public Builder swamp (String swamp) {
this . swamp = swamp ; return this;
}
@Override public
Ogre build () {
null ) {
throw Internal. missingRequiredFields ( name , "name" ) ;
}
return new Ogre( name , layers , swamp , super .buildUnknownFields()) ;
} }
class Ogre @JvmOverloads constructor (
@JvmField val name : String , @JvmField val layers : List<Int>
@JvmField val
swamp : String?
unknownFields: ByteString = ByteString. EMPTY ) : Message<Ogre , Ogre.Builder>( ADAPTER , unknownFields)
@JvmField val name : String , @JvmField val layers : List<Int> = emptyList () , @JvmField val swamp : String? = null ,
val shrek = Ogre(
name = "shrek" ,
layers = listOf ( 1 , 2 ) ,
swamp = null )
Ogre shrek = new Ogre() ;
Ogre shrek = new Ogre( "Shrek" , Arrays. asList ( 1 , 2 ) , "Shrek" ) ;
Java Interop
class
Ogre(
@JvmField val name : String , @JvmField val layers : List<Int> = emptyList () , @JvmField val swamp : String? = null
) interface
@JvmField val name : String , @JvmField val layers : List<Int> = emptyList () , @JvmField val swamp : String? = null
interface Ogre {
val name : String
val layers : List<Int>
val swamp : String? }
interface Ogre {
val name : String
val layers : List<Int>
val swamp : String? }
shrek.getLayers() ;
inline fun < reified T
Ogre. findFriendOfType (): T ? {
for (friend in friends ()) {
if (friend is T ) return friend }
return null }
inline fun < reified T
Ogre. findFriendOfType (): T ? {
for (friend in friends ()) {
if (friend is T ) return friend }
return null } shrek.findFriendOfType<Donkey>()
inline fun < reified T
Ogre. findFriendOfType (): T ? {
for (friend in friends ()) {
if (friend is T ) return friend }
return null } shrek.findFriendOfType<Donkey>()
shrek.<Donkey>findFriendOfType() ;
inline fun < reified T
Ogre. findFriendOfType (): T ? {
for (friend a in friends ()) {
if (friend is T ) return friend } Y
return b null } Z
fun < T
Ogre. findFriendOfType (type: Class< T ): T ? {
for (friend in friends ()) {
if (type.isInstance(friend)) return friend as T ? } B
return null } A
inline fun < reified T
Ogre. findFriendOfType (): T ? {
for (friend a in friends ()) {
if (friend is T ) return friend } Y
return b null } Z
findFriendOfType ( ::class. java )
fun < T
Ogre. findFriendOfType (type: Class< T ): T ? {
for (friend in friends ()) {
if (type.isInstance(friend)) return friend as T ? } B
return null } A
inline fun < reified T
Ogre. findFriendOfType (): T ? {
return b findFriendOfType ( T :: class . java ) } Z
interface SwampChangedListener {
fun swampChanged (newSwamp: String) } fun addSwampChangedListener (listener: SwampChangedListener) = …
interface SwampChangedListener {
fun swampChanged (newSwamp: String) } A
fun addSwampChangedListener (listener: SwampChangedListener) = …
shrek.addSwampChangedListener( new SwampChangedListener() {
@Override public void swampChanged ( @NotNull String newSwamp) { P
System.
out .println( "What are you doing in "
} }) ;
interface SwampChangedListener {
fun swampChanged (newSwamp: String) } A
fun addSwampChangedListener (listener: SwampChangedListener) = …
shrek.addSwampChangedListener(newSwamp -> { P
System. out .println( "What are you doing in "
interface SwampChangedListener {
fun swampChanged (newSwamp: String) } fun addSwampChangedListener (listener: SwampChangedListener) = …
interface SwampChangedListener {
fun swampChanged (newSwamp: ( String) : Unit
} fun addSwampChangedListener (listener: SwampChangedListener) = … shrek.addSwampChangedListener( object : SwampChangedListener {
override fun swampChanged (newSwamp: String) { System. out .println( "What are you doing in $ newSwamp " ) } }) KT-7770
fun addSwampChangedListener (listener: (String) -> Unit) = …
fun addSwampChangedListener (listener: (String) -> Unit) = …
shrek.addSwampChangedListener { newSwamp ->
System. out .println( "What are you doing in $ newSwamp " ) }
fun addSwampChangedListener (listener: (String) -> Unit) = …
shrek.addSwampChangedListener { newSwamp ->
System. out .println( "What are you doing in $ newSwamp " ) }
shrek.addSwampChangedListener(newSwamp -> { System. out .println( "What are you doing in "
fun addSwampChangedListener (listener: SwampChangedListener) = …
public interface SwampChangedListener {
void swampChanged (String newSwamp) ; } Z
fun addSwampChangedListener (listener: SwampChangedListener) = …
shrek.addSwampChangedListener(SwampChangedListener { newSwamp ->
System. out .println( "What are you doing in $ newSwamp " ) } )
public interface SwampChangedListener {
void swampChanged (String newSwamp) ; } Z
fun addSwampChangedListener (listener: SwampChangedListener) = … public interface SwampChangedListener {
void swampChanged (String newSwamp) ; } Z
shrek.addSwampChangedListener(newSwamp -> { System. out .println( "What are you doing in "
System. out .println("What are you doing in $newSwamp") } )
sealed class Optional< T : Any>
data class Some< T : Any>( val value : T ): Optional< T
() object None : Optional<Nothing>()
sealed class Optional< T : Any>
data class Some< T : Any>( val value : T ): Optional< T
() object None : Optional<Nothing>()
null ) None else Some( this )
@file:JvmName ( "Optionals" )
sealed class Optional< T : Any>
data class Some< T : Any>( val value : T ): Optional< T
() object None : Optional<Nothing>()
@JvmName ( "ofNullable" )
null ) None else Some( this )
sealed class Optional< T : Any> {
companion object {
@JvmName ( "ofNullable" ) @JvmStatic fun < T
:
Any> T ?. asOptional ()
=
null ) None else Some( this )
} Y
} Z
data class Some< T : Any>( val value : T ): Optional< T
() object None : Optional<Nothing>() @file:JvmName("Optionals ") KT-15286
sealed class Optional< T : Any> {
companion object {
@JvmStatic fun < T
:
Any> ofNullable (value: T ?) = value. asOptional () } Y
} Z
data class Some< T : Any>( val value : T ): Optional< T
() object None : Optional<Nothing>() fun < T
:
null ) None else Some( this ) @JvmName KT-15286
@file:JvmName( "-Optionals" ) sealed class Optional< T : Any> {
companion object {
@JvmStatic fun < T
:
Any> ofNullable (value: T ?) = value. asOptional () } Y
} Z
data class Some< T : Any>( val value : T ): Optional< T
() object None : Optional<Nothing>() fun < T
:
null ) None else Some( this ) KT-15286
class Foo (
val bar : Nothing , val listBar : List<Nothing> )
class Foo (
val bar : Nothing , val listBar : List<Nothing> ) Void bar = foo.getBar() ; List listBar = foo.getListBar() ;
KotlinPoet
Type
Type Class
Type Class Parameterized Type
Type String Map<String,Int>
val stringClass: KClass<String> = String:: class
val stringClass: KClass<String> = String:: class val stringName: ClassName = stringClass. asClassName ()
val stringClass: KClass<String> = String:: class val stringName: ClassName = stringClass. asClassName ()
import kotlin.String val foo : String = ""
val stringClass: KClass<String> = String:: class val stringName: ClassName = stringClass. asClassName ()
import kotlin.String val foo : String = ""
class String
val stringClass: KClass<String> = String:: class val stringName: ClassName = stringClass. asClassName ()
class String {
val foo : kotlin.String = "" }
val stringClass: KClass<String> = String:: class val stringName: ClassName = stringClass. asClassName ()
val stringClass: KClass<String> = String:: class val stringName: ClassName = stringClass. asClassName ()
val mapStringToInt
= ParameterizedTypeName.get( Map:: class . asTypeName () , stringName , Int:: class . asTypeName ())
val stringClass: KClass<String> = String:: class val stringName: ClassName = stringClass. asClassName ()
val mapStringToInt
= ParameterizedTypeName.get( Map:: class . asTypeName () , stringName , Int:: class . asTypeName ())
val nullableMap = mapStringToInt.asNullable()
val foo = PropertySpec.builder( "foo" , String:: class ) .initializer( "%S" , "foo" ) .build()
val foo = PropertySpec.builder( "foo" , String:: class ) .initializer( "%S" , "foo" ) .build()
String:: class
val foo = PropertySpec.builder( "foo" , String:: class ) .initializer( "%S" , "foo" ) .build()
"%S" ,
"foo"
val foo = PropertySpec.builder( "foo" , String:: class ) .initializer( "%S" , "foo" ) .build()
val foo = PropertySpec.builder( "foo" , String:: class ) .initializer( "%S" , "foo" ) .build()
println (foo) val
foo : kotlin.String = "foo" X
val foo = PropertySpec.builder( "foo" , String:: class ) .initializer( "%S" , "foo
bar" ) .build()
println (foo) val
foo : kotlin.String = "foo
bar" X
val foo = PropertySpec.builder( "foo" , String:: class ) .initializer( "%S" , "foo
bar" ) .build()
println (foo) val
foo : kotlin.String = "foo
bar" X
kotlin.String
val foo = PropertySpec.builder( "foo" , String:: class ) .initializer( "%S" , "foo
bar" ) .build()
val file = FileSpec.builder( "com.example" , "KotlinConf.kt" ) .addProperty(foo) .build()
println (file)
package com.example import kotlin.String val
foo : String = "foo
bar" X
foo
PropertySpec.builder( "foo" , String:: class ) .initializer( "%S" , "foo
bar" ) .build() package com.example import kotlin.String val
foo : String = "foo
bar" X
FunSpec.builder( "main" ) .addParameter( "args" , String:: class, VARARG ) .build() package com.example import kotlin.String fun main ( vararg args: String)
{ }
TypeSpec.classBuilder( "User" ) .addModifiers( DATA ) .build() package com.example data class User
TypeSpec.classBuilder( "User" ) .addModifiers( DATA ) .build() package com.example data class User
TypeSpec.classBuilder( "User" ) .addModifiers( DATA ) .addProperty(PropertySpec.builder( "name" , String:: class ).build()) .build() Z
package com.example data class User { Y
val
name : String } X
TypeSpec.classBuilder( "User" ) .addModifiers( DATA ) .addProperty(PropertySpec.builder( "name" , String:: class ).build())
.primaryConstructor(FunSpec.constructorBuilder() .addParameter( "name" , String:: class ) .build()) A
.build()
Z
package com.example data class User(name: String) G { Y
val
name : String } X
name: String
TypeSpec.classBuilder( "User" ) .addModifiers( DATA ) .addProperty(PropertySpec.builder( "name" , String:: class )
.initializer(
"name" ) .build()) B
.primaryConstructor(FunSpec.constructorBuilder() .addParameter( "name" , String:: class ) .build()) A
.build()
package com.example data class User( val
name : String) G
TypeSpec.classBuilder( "User" ) .addModifiers( DATA ) .addProperty(PropertySpec.builder( "name" , String:: class )
.initializer(
"name.toLowerCase()" ) .build()) B
.primaryConstructor(FunSpec.constructorBuilder() .addParameter( "name" , String:: class ) .build()) A
.build()
package com.example data class User(name: String) G {
val
name : String = name. toLowerCase () } X
FunSpec.builder( "seconds" ) .receiver(Long:: class ) .returns(Duration:: class ) .addStatement( "return %T.ofSeconds(this)" , Duration:: class ) .build() package com.example import java.time.Duration
import kotlin.Long
fun Long. seconds (): Duration = Duration.ofSeconds( this )
FunSpec.builder( "seconds" ) .receiver(Long:: class ) .returns(Duration:: class )
.addStatement(
"require(this >= 0L)" )
.addStatement(
"return %T.ofSeconds(this)" , Duration:: class ) .build() package com.example import java.time.Duration
import kotlin.Long
fun Long. seconds (): Duration {
require ( this
= 0L )
return Duration.ofSeconds( this )
}
FunSpec.builder( "seconds" ) .receiver(Long:: class ) .returns(Duration:: class )
.addStatement(
"require(this >= 0L)" )
.addStatement(
"return %T.ofSeconds(this)" , Duration:: class ) .build()
val longSeconds = FunSpec.builder( "seconds" ) .receiver(Long:: class ) .returns(Duration:: class )
.addStatement(
"require(this >= 0L)" )
.addStatement(
"return %T.ofSeconds(this)" , Duration:: class ) .build()
val longSeconds = FunSpec.builder( "seconds" ) .receiver(Long:: class ) .returns(Duration:: class )
.addStatement(
"require(this >= 0L)" )
.addStatement(
"return %T.ofSeconds(this)" , Duration:: class ) .build()
FunSpec.builder( "main" ) .addParameter( "args" , String:: class,
VARARG ) .addStatement( "println(%L.%N())" ,
2L , longSeconds) .build()
val longSeconds = FunSpec.builder( "seconds" ) .receiver(Long:: class ) .returns(Duration:: class )
.addStatement(
"require(this >= 0L)" )
.addStatement(
"return %T.ofSeconds(this)" , Duration:: class ) .build()
FunSpec.builder( "main" ) .addParameter( "args" , String:: class,
VARARG ) .addStatement( "println(%L.%N())" ,
2L , longSeconds) .build()
%N
longSeconds
val longSeconds = FunSpec.builder( "seconds" ) .receiver(Long:: class ) .returns(Duration:: class )
.addStatement(
"require(this >= 0L)" )
.addStatement(
"return %T.ofSeconds(this)" , Duration:: class ) .build()
FunSpec.builder( "main" ) .addParameter( "args" , String:: class,
VARARG ) .addStatement( "println(%L.%N())" ,
2L , longSeconds) .build() fun
main ( vararg args: String) {
println ( 2L . seconds ()) }
val code = CodeBlock.builder()
val code = CodeBlock.builder() code.addStatement( "val foo = %T.MIN_VALUE" , Int:: class )
val code = CodeBlock.builder() code.addStatement( "val foo = %T.MIN_VALUE" , Int:: class )
code.add( "val bar = " ) when (answer) {
YES -> code.add( "0L" )
NO -> code.add( "%T.MIN_VALUE" , Int:: class ) } code.add( ".toString()
" )
val code = CodeBlock.builder() code.addStatement( "val foo = %T.MIN_VALUE" , Int:: class )
code.add( "val bar = " ) when (answer) {
YES -> code.add( "0L" )
NO -> code.add( "%T.MIN_VALUE" , Int:: class ) } code.add( ".toString()
" )
code.beginControlFlow( "if (bar.isEmpty())" ) .addStatement( "println(%S)" , "Empty!" ) .nextControlFlow( "else" ) .addStatement( "println(bar)" ) .endControlFlow()
val intMin = CodeBlock.of( "%T.MIN_VALUE" , Int:: class ) val intMax = CodeBlock.of( "%T.MAX_VALUE" , Int:: class ) val longMin = CodeBlock.of( "%T.MIN_VALUE" , Long:: class ) val longMax = CodeBlock.of( "%T.MAX_VALUE" , Long:: class ) val values = listOf (intMin , intMax , longMin , longMax)
val intMin = CodeBlock.of( "%T.MIN_VALUE" , Int:: class ) val intMax = CodeBlock.of( "%T.MAX_VALUE" , Int:: class ) val longMin = CodeBlock.of( "%T.MIN_VALUE" , Long:: class ) val longMax = CodeBlock.of( "%T.MAX_VALUE" , Long:: class ) val values = listOf (intMin , intMax , longMin , longMax) // elsewhere val list = values. joinToCode ( prefix = "listOf(" , suffix = ")" )
val intMin = CodeBlock.of( "%T.MIN_VALUE" , Int:: class ) val intMax = CodeBlock.of( "%T.MAX_VALUE" , Int:: class ) val longMin = CodeBlock.of( "%T.MIN_VALUE" , Long:: class ) val longMax = CodeBlock.of( "%T.MAX_VALUE" , Long:: class ) val values = listOf (intMin , intMax , longMin , longMax) // elsewhere val list = values. joinToCode ( prefix = "listOf(" , suffix = ")" )
listOf (Int. MIN_VALUE , Int. MAX_VALUE , Long. MIN_VALUE , Long. MAX_VALUE )
inline fun < reified T , R : CharSequence>
(String.() ->
R ). crazy ( noinline foo: T .( R ?) -> Unit)
where T : Runnable , T : Closeable
=
42L
val typeT = TypeVariableName( "T" , Runnable:: class, Closeable:: class ) val typeR = TypeVariableName( "R" , CharSequence:: class ) val stringExtToR = LambdaTypeName.get(String:: class . asClassName () , returnType = typeR) val tRtoUnit = LambdaTypeName.get(typeT ,
parameters = typeR.asNullable() , returnType = UNIT ) val crazy = FunSpec.builder( "crazy" ) .addModifiers( INLINE ) .receiver(stringExtToR) .addTypeVariable(typeT.reified()) .addTypeVariable(typeR) .addParameter( "foo" , tRtoUnit , NOINLINE ) .addStatement( "return 42L" ) .build()
inline fun < reified T , R : CharSequence>
(String.() ->
R ). crazy ( noinline foo: T .( R ?) -> Unit)
where T : Runnable , T : Closeable
=
42L
Kotlin Compatible Code
@Nullable public String getSwamp () {
return swamp ; }
@Nullable public String getSwamp () {
return swamp ; }
val swamp: String? = shrek. swamp
Bytecode Build tool
Bytecode Build tool
interface Foo {
val bar : String }
public abstract interface com/sample/Foo {
// access flags 0x401
public abstract getBar()Ljava/lang/String ;
@Lorg/jetbrains/annotations/NotNull ; () // invisible
LOCALVARIABLE
this Lcom/sample/Foo ; L0 L1 0
@Lkotlin/Metadata ; ( mv={ 1 ,
1 ,
7 } , bv={ 1 ,
0 ,
2 } , k= 1 , d1={ “…” } , d2={ "Lcom/sample/Foo;" ,
"" ,
"bar" ,
"" ,
“getBar" }
)
// compiled from: Foo.kt
}
public abstract interface com/sample/Foo {
// access flags 0x401
public abstract getBar()Ljava/lang/String ;
@Lorg/jetbrains/annotations/NotNull ; () // invisible
LOCALVARIABLE
this Lcom/sample/Foo ; L0 L1 0
@Lkotlin/Metadata ; ( mv={ 1 ,
1 ,
7 } , bv={ 1 ,
0 ,
2 } , k= 1 , d1={ “…” } , d2={ "Lcom/sample/Foo;" ,
"" ,
"bar" ,
"" ,
“getBar" }
)
// compiled from: Foo.kt
} goo.gl/GcT9gz
github.com/Takhion/kotlin-metadata
org.jetbrains.kotlin.serialization .ProtoBuf.Class
github.com/Takhion/kotlin-metadata
org.jetbrains.kotlin.serialization .ProtoBuf.Class
github.com/Takhion/kotlin-metadata
org.jetbrains.kotlin.serialization .ProtoBuf.Class
github.com/Takhion/kotlin-metadata
org.jetbrains.kotlin.serialization .ProtoBuf.Class
github.com/Takhion/kotlin-metadata
org.jetbrains.kotlin.serialization .ProtoBuf.Class
github.com/Takhion/kotlin-metadata
org.jetbrains.kotlin.serialization .ProtoBuf.Class
public abstract interface com/sample/Foo {
// access flags 0x401
public abstract
getBar ()Ljava/lang/String ;
@Lorg/jetbrains/annotations/NotNull ; () // invisible
LOCALVARIABLE
this Lcom/sample/Foo ; L0 L1 0
@Lkotlin/Metadata ; ( mv={ 1 ,
1 ,
7 } , bv={ 1 ,
0 ,
2 } , k= 1 , d1={ “…” } , d2={ "Lcom/sample/Foo;" ,
"" ,
"bar" ,
"" ,
“ getBar " }
)
// compiled from: Foo.kt
}
Bytecode
Bytecode
public abstract interface com/sample/Foo {
// access flags 0x401
public abstract getBar()Ljava/lang/String ;
@Lorg/jetbrains/annotations/NotNull ; () // invisible
LOCALVARIABLE
this Lcom/sample/Foo ; L0 L1 0
@Lkotlin/Metadata ; ( mv={ 1 ,
1 ,
7 } , bv={ 1 ,
0 ,
2 } , k= 1 , d1={ “…” } , d2={ "Lcom/sample/Foo;" ,
"" ,
"bar" ,
"" ,
“getBar" } ) g
// compiled from: Foo.kt
} A
public abstract interface com/sample/Foo {
// access flags 0x401
public abstract getBar()Ljava/lang/String ;
@Lorg/jetbrains/annotations/NotNull ; () // invisible
LOCALVARIABLE
this Lcom/sample/Foo ; L0 L1 0
@Lkotlin/Metadata ; ( mv={ 1 ,
1 ,
7 } , bv={ 1 ,
0 ,
2 } , k= 1 , d1={ “…” } , d2={ "Lcom/sample/Foo;" ,
"" ,
"bar" ,
"" ,
“getBar" } ) g
// compiled from: Foo.kt
} A
public abstract interface com/sample/Foo {
// access flags 0x401
public abstract getBar()Ljava/lang/String ;
@Lorg/jetbrains/annotations/NotNull ; () // invisible
LOCALVARIABLE
this Lcom/sample/Foo ; L0 L1 0
@Lkotlin/Metadata ; ( mv={ 1 ,
1 ,
7 } , bv={ 1 ,
0 ,
2 } , k= 1 , d1={ “…” } , d2={ "Lcom/sample/Foo;" ,
"" ,
"bar" ,
"" ,
“getBar" }
)
// compiled from: Foo.kt
} { A
AnnotationVisitor av1 = av0.visitArray( "d2" ) ;
av1.visit( null, "Lcom/sample/Foo;" ) ;
av1.visit( null, "" ) ;
av1.visit( null, "bar" ) ;
av1.visit( null, "" ) ;
av1.visit( null, "getBar" ) ;
av1.visit( null, "()I" ) ;
av1.visitEnd() ; } B
{ C
mv = cw.visitMethod( ACC_PUBLIC + ACC_ABSTRACT ,
"getBar" , "()I" , null, null ) ;
mv.visitEnd() ; } D
{ A
AnnotationVisitor av1 = av0.visitArray( "d2" ) ;
av1.visit( null, "Lcom/sample/Foo;" ) ;
av1.visit( null, "" ) ;
av1.visit( null, "bar" ) ;
av1.visit( null, "" ) ;
av1.visit( null, "getBar" ) ;
av1.visit( null, "()I" ) ;
av1.visitEnd() ; } B
{ C
mv = cw.visitMethod( ACC_PUBLIC + ACC_ABSTRACT ,
"getBar" , "()I" , null, null ) ;
mv.visitEnd() ; } D b
b
{ A
AnnotationVisitor av1 = av0.visitArray( "d2" ) ;
av1.visit( null, "Lcom/sample/Foo;" ) ;
av1.visit( null, "" ) ;
av1.visit( null, "bar" ) ;
av1.visit( null, "" ) ;
av1.visit( null, " bar " ) ;
av1.visit( null, "()I" ) ;
av1.visitEnd() ; } B
{ C
mv = cw.visitMethod( ACC_PUBLIC + ACC_ABSTRACT ,
" bar " , "()I" , null, null ) ;
mv.visitEnd() ; } D
{ A
AnnotationVisitor av1 = av0.visitArray( "d2" ) ;
av1.visit( null, "Lcom/sample/Foo;" ) ;
av1.visit( null, "" ) ;
av1.visit( null, "bar" ) ;
av1.visit( null, "" ) ;
av1.visit( null, " bar " ) ;
av1.visit( null, "()I" ) ;
av1.visitEnd() ; } B
{ C
mv = cw.visitMethod( ACC_PUBLIC + ACC_ABSTRACT ,
" bar " , "()I" , null, null ) ;
mv.visitEnd() ; } D
{ AnnotationVisitor av1 = av0.visitArray( "d2" ) ;
av1.visit( null, "Lcom/sample/Foo;" ) ;
av1.visit( null, "" ) ;
av1.visit( null, "bar" ) ;
av1.visit( null, "" ) ;
av1.visit( null, " bar " ) ;
av1.visit( null, "()I" ) ;
av1.visitEnd() ; } { mv = cw.visitMethod( ACC_PUBLIC + ACC_ABSTRACT ,
" bar " , "()I" , null, null ) ;
mv.visitEnd() ; } public abstract interface com/sample/Foo {
// access flags 0x401
public abstract
bar ()Ljava/lang/String ;
@Lorg/jetbrains/annotations/NotNull ; () // invisible
LOCALVARIABLE
this Lcom/sample/Foo ; L0 L1 0
@Lkotlin/Metadata ; ( mv={ 1 ,
1 ,
7 } , bv={ 1 ,
0 ,
2 } , k= 1 , d1={ “…” } , d2={ "Lcom/sample/Foo;" ,
"" ,
"bar" ,
"" ,
“ bar ” }
)
// compiled from: Foo.kt
}
class KotlinFoo( override val bar: Int): Foo class JavaFoo implements Foo { @Override
public int bar() {
return 0 ;
} }
void setPadding ( int l , int t , int r , int b) {
// … }
void setPadding ( int l , int t , int r , int b) {
// … } z
view.setPadding( 10 , 0 , 0 , 10 )
void setPadding ( int l , int t , int r , int b) {
// … } z
view.setPadding( left = 10 , bottom = 10 )
Bytecode
Multiplatform
Bytecode
Bytecode
Bytecode LLVM
enum class Direction { NORTH , SOUTH , EAST , WEST } class GamePeice( movement: Set<Direction> = EnumSet. of (Direction. NORTH ) ) Z
enum class Direction { NORTH , SOUTH , EAST , WEST } class GamePeice( movement: Set<Direction> = EnumSet. of (Direction. NORTH ) ) Z EnumSet. of
import java.util.EnumSet enum class Direction { NORTH , SOUTH , EAST , WEST } class GamePeice( movement: Set<Direction> = EnumSet. of (Direction. NORTH ) ) Z
s O
EnumSet.
of
enum class Direction { NORTH , SOUTH , EAST , WEST } class GamePeice( movement: Set<Direction> = setOf (Direction. NORTH ) ) Z
S o
import com.google.common.collect
@AutoImplement interface Party {
val people : ImmutableList<Person> }
import com.google.common.collect
@AutoImplement interface Party {
val people : ImmutableList<Person> }
import com.google.common.collect
@Generated class AutoParty( override val people : ImmutableList<Person>) : Party
CREATE TABLE user(
name TEXT NOT NULL,
location TEXT AS android.location.Location )
CREATE TABLE user(
name TEXT NOT NULL,
location TEXT AS android.location.Location ) import android.location.Location data class User(
val
name : String,
val
location : Location )
@file:JvmName ( "ByteStrings" ) @JvmName ( "from" ) fun ByteArray. asByteString (): ByteString = …
@file:JvmName ( "ByteStrings" ) @JvmName ( "from" ) fun ByteArray. asByteString (): ByteString = …
byte [] bytes = …
ByteString b = ByteStrings. from (bytes) ;
@file:JvmName ( "ByteStrings" ) @JvmName ( "from" ) fun ByteArray. asByteString (): ByteString = …
byte [] bytes = …
ByteString b = ByteStrings. from (bytes) ; Cannot access 'JvmName': it is internal in 'kotlin.jvm' s
KT-19507
@JsName ( "from" ) fun ByteArray. asByteString (): ByteString = … @file:JvmName("ByteStrings")
@ JsName ( "from" ) fun ByteArray. asByteString (): ByteString = … @file:JvmName("ByteStrings")
KT-19508
Verbosity is okay. API is the #1 priority.
Verbosity is okay. API is the #1 priority. If you do any kind of Java codegen, keep Kotlin in mind.
Verbosity is okay. API is the #1 priority. If you do any kind of Java codegen, keep Kotlin in mind. Don’t depend on platform types unless the user does.
KotlinPoet 0.6.0 released!
@Strongolopolis & @JakeWharton Kotlin Code Generation
Kotlin provides simpler options than traditional Java patterns like builders and factories often found in generated code. By using Kotlin to generate an API, you can not only create a pleasant experience from both languages, but also unlock the possibility of targeting native and JS. This talk will cover the tools needed to generate Kotlin code and also the features available in Kotlin that can improve your generated code.
Presented with Alec Strong
for free. You
can too.