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Swift & Kotlin
2017/9/16
ezura
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ezura (@eduraaa)
• iOS engineer @ LINE
• like: programming
• mock mock radio
• ΪϦγϟֶ / Swift
• Blending Kotlin's culture into Swift
• ఈ͔ΒֶͿ Swift
• …
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official on Android
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Kotlin
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Kotlin
OOP
extension
interface
default
implementati
on
generics
delegation
null
safety
tailrec
static
type
Java
GC
sealed
class
variance
declaration
object
JS
companion
object
if, when
expression
Type
inference
(Corout
ines)
inline
annotation
FP
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• Started in 2010
• Object-oriented programming
• Support functional programming
• Static typing
• Type inference
• Null safety
• Generic programming
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Kotlin’s background
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started in 2010
first official 1.0 release in 2016
Let's make a new language
based on the knowledge
that has developed IDEs
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class Class: Super() {
var property = ""
fun method() {
var nullable: String? = null
if (nullable != null) {
nullable.length
}
val list = listOf(1, 2, 3)
list.forEach { print(it) }
}
}
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class Class: Super() {
var property = ""
fun method() {
var nullable: String? = null
if (nullable != null) {
nullable.length
}
val list = listOf(1, 2, 3)
list.forEach { print(it) }
}
}
Object-oriented programming
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class Class: Super() {
var property = ""
fun method() {
var nullable: String? = null
if (nullable != null) {
nullable.length
}
val list = listOf(1, 2, 3)
list.forEach { print(it) }
}
} Support functional programming
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class Class: Super() {
var property = ""
fun method() {
var nullable: String? = null
if (nullable != null) {
nullable.length
}
val list = listOf(1, 2, 3)
list.forEach { print(it) }
}
}
Static typing
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class Class: Super() {
var property = ""
fun method() {
var nullable: String? = null
if (nullable != null) {
nullable.length
}
val list = listOf(1, 2, 3)
list.forEach { print(it) }
}
}
Type inference
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class Class: Super() {
var property = ""
fun method() {
var nullable: String? = null
if (nullable != null) {
nullable.length
}
val list = listOf(1, 2, 3)
list.forEach { print(it) }
}
}
Generic programming
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class Class: Super() {
var property = ""
fun method() {
var nullable: String? = null
if (nullable != null) {
nullable.length
}
val list = listOf(1, 2, 3)
list.forEach { print(it) }
}
}
Null safety
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• Started in 2010
• Object-oriented programming
• Support functional programming
• Static typing
• Type inference
• Null safety
• Generic programming
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• Started in 2010
• Object-oriented programming
• Support functional programming
• Static typing
• Type inference
• Null safety
• Generic programming
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Swift ͱ Kotlin ࣅ͍ͯΔʁʁ
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Swift ͱ Kotlin ࣅ͍ͯΔʁʁ
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Swift ͱ Kotlin ࣅ͍ͯΔʁʁ
❌ runtime environment
❌ memory management
❌ background
❌ calling Java/Objective-C
❌ Culture
❌ features
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Swift ͱ Kotlin ࣅ͍ͯΔʁʁ
Is the learning cost low?
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Swift ͱ Kotlin ࣅ͍ͯΔʁʁ
෦͋Δ
Is the learning cost low?
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Swift ͱ Kotlin ࣅ͍ͯΔʁʁ
෦͋Δ
Is the learning cost low?
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Kotlin ֶश
Swift ࣝͰϒʔετՄೳ
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Index
• What is Kotlin
• Is Kotlin like Swift?
• some keyword
• some features
• Traps
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Index
• What is Kotlin
• Is Kotlin like Swift?
• some keyword
• some features
• Traps
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Syntax
Swift Kotlin
var, let
func f(arg: Any) -> Any
class AnyType { … }
var obj = Obj()
obj.method(arg: v)
var, val
fun f(arg: Any): Any
class AnyType { … }
var obj = Obj()
obj.method(v)
see also: http://nilhcem.com/swift-is-like-kotlin/
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Support functional programming
Swift Kotlin
val f = { x: Int ->
/* … */
}
obj.map { /* … */ }
let f = { Int -> String in
/* … */
}
obj.map { /* … */ }
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Support functional programming
Swift Kotlin
val f = { x: Int ->
/* … */
}
obj.map { /* … */ }
let f = { Int -> String in
/* … */
}
obj.map { /* … */ }
constant constant
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Support functional programming
Swift Kotlin
val f = { x: Int ->
/* … */
}
obj.map { /* … */ }
let f = { Int -> String in
/* … */
}
obj.map { /* … */ }
first class function first class function
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Support functional programming
Swift Kotlin
val f = { x: Int ->
/* … */
}
obj.map { /* … */ }
let f = { Int -> String in
/* … */
}
obj.map { /* … */ }
higher-order function higher-order function
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Null safety
Swift Kotlin
let i: Int?
i?.description
if let i = i {
i.description
}
val i: Int?
i?.toString()
if (i != null) {
i.toString()
}
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Null safety
Swift Kotlin
let i: Int?
i?.description
if let i = i {
i.description
}
val i: Int?
i?.toString()
if (i != null) {
i.toString()
}
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extension
Swift Kotlin
extension String {
func f() {}
var v: String { return "" }
}
let string = ""
string.f()
string.v
fun String.f() = {}
val String.v: String get() = ""
val string = ""
string.f()
string.v
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default implementation
for protocol/interface
Swift Kotlin
protocol P {
func f()
}
extension P {
func f() {
/* do something */
}
}
interface I {
fun f() {
/* do something */
}
}
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• Started in 2010
• Object-oriented programming
• Support functional programming
• Static typing
• Type inference
• Null safety
• Generic programming
• Some syntax
• Extension
• Default implementation
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Kotlin
OOP
extension
interface
default
implementati
on
generics
delegation
null
safety
tailrec
static
type
Java
GC
sealed
class
variance
declaration
object
JS
companion
object
if, when
expression
Type
inference
(Corout
ines)
inline
annotation
FP
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Kotlin
OOP
extension
interface
default
implementati
on
generics
delegation
null
safety
tailrec
static
type
Java
GC
sealed
class
variance
declaration
object
JS
companion
object
if, when
expression
Type
inference
(Corout
ines)
inline
annotation
FP
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Trap
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extension
Swift Kotlin
extension String {
func f() {}
var v: String { return "" }
}
fun String.f() = {}
val String.v: String get() = “"
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extension
Type Type
function
property
function
property
Swift Kotlin
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extension
Type Type
function
property
function
property
Swift Kotlin
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extension
function
Util class
instance
static Result method(Some target)
Some
Type
Java
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extension
Util.method(instance)
Java
function
Util class
instance
Some
Type
static Result method(Some target)
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extension
Collections.max(list)
Java
function
Util class
instance
Some
Type
static Result method(Some target)
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extension
max(list)
Java
function
Util class
instance
Some
Type
static Result method(Some target)
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extension
max(list)
Java
function
Util class
instance
Some
Type
list.max()
want to …
static Result method(Some target)
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extension
Some
Type
function
property
Kotlin
Util.extensionMethod(instance)
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extension
Some
Type
function
property
Kotlin
obj.extensionMethod()
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extension
Type Type
function
property
function
property
Swift Kotlin
extend type by
functions/properties
add
functions/properties
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extension
Type Type
function
property
function
property
Swift Kotlin
protocol interface
extension String: MyProtocol {
/* ... */
}
-
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extension
Type Type
function
property
function
property
Swift Kotlin
extend type by
functions/properties
add
functions/properties
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default implementation
for protocol/interface
Swift Kotlin
protocol P {
func f()
}
extension P {
func f() {
/* do something */
}
}
interface I {
fun f() {
/* do something */
}
}
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default implementation
for protocol/interface
Swift Kotlin
protocol P {
func f()
}
extension P {
func f() {
/* do something */
}
}
interface I {
fun f() {
/* do something */
}
}
P f()
extension P
f()
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default implementation
for protocol/interface
Swift Kotlin
protocol P {
func f()
}
extension P {
func f() {
/* do something */
}
}
interface I {
fun f()
}
fun I.f() {
/* do something */
}
P f()
extension extension
P f()
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default implementation
for protocol/interface
Swift Kotlin
protocol P {
func f()
}
extension P {
func f() {
/* do something */
}
}
interface I {
fun f()
}
fun I.f() {
/* do something */
}
class A: I {} // error
P f()
extension extension
P f()
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default implementation
for protocol/interface
Swift Kotlin
protocol P {
func f()
}
extension P where … {
func f() {
/* do something */
}
}
interface I {
fun f() {
/* do something */
}
}
P f()
extension
where …
P
f()
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default implementation
for protocol/interface
Protocol
Interface
Implementation
Implementation
extension
Swift Kotlin
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Null safety
Swift Kotlin
let i: Int?
i?.description
if let i = i {
i.description
}
val i: Int?
i?.toString()
if (i != null) {
i.toString()
}
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Null safety
Swift Kotlin
let i: Int?
i?.description
if let i = i {
i.description
}
val i: Int?
i?.toString()
if (i != null) {
i.toString()
}
Optional Nullable
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Null safety
Swift Kotlin
enum Optional {
case none
case some(Wrapped)
}
nullable
Optional Nullable
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Null safety
Swift Kotlin
enum Optional {
case none
case some(Wrapped)
}
nullable
exist some value
or not null or not null
Optional Nullable
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Null safety
Swift Kotlin
ɹ
exist some value
or not not null or null
Value none
or Value or null
Optional Nullable
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Null safety
Swift Kotlin
ɹ
exist some value
or not not null or null
Value none
or Value or null
Optional Nullable
Value = Int?
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Null safety
Swift Kotlin
ɹ
exist some value
or not not null or null
Int? none
or Int? or null
Optional Nullable
Value = Int?
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Null safety
Swift Kotlin
ɹ
exist some value
or not not null or null
1
or
nil
none
or 1
or
null
or null
Optional Nullable
Value = Int?
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Null safety
Swift Kotlin
ɹ
exist some value
or not not null or null
.some
(nil) none
or or null
null
??
Optional Nullable
Value = Int?
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Some familiar functions
Swift Kotlin
[1, 2, 3].forEach {
if $0 == 2 { return }
print($0)
}
listOf(1, 2, 3).forEach {
if (it == 2) { return }
println(it)
}
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Some familiar functions
Swift Kotlin
[1, 2, 3].forEach {
if $0 == 2 { return }
print($0)
}
listOf(1, 2, 3).forEach {
if (it == 2) { return }
println(it)
}
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[1, 2, 3].forEach {
if $0 == 2 { return }
print($0)
}
listOf(1, 2, 3).forEach {
if (it == 2) { return }
println(it)
}
Some familiar functions
Swift Kotlin
1
3
1
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[1, 2, 3].forEach {
if $0 == 2 { return }
print($0)
}
listOf(1, 2, 3).forEach {
if (it == 2) { return }
println(it)
}
Some familiar functions
Swift Kotlin
1
3
1
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Some familiar functions
Swift Kotlin
@_inlineable
public func forEach(
_ body: (Element) throws -> Void
) rethrows {
for element in self {
try body(element)
}
}
public inline fun
Iterable.forEach(action: (T) -> Unit): Unit {
for (element in this) action(element)
}
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Some familiar functions
Swift Kotlin
@_inlineable
public func forEach(
_ body: (Element) throws -> Void
) rethrows {
for element in self {
try body(element)
}
}
public inline fun
Iterable.forEach(action: (T) -> Unit): Unit {
for (element in this) action(element)
}
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Some familiar functions
Swift Kotlin
@_inlineable
public func forEach(
_ body: (Element) throws -> Void
) rethrows {
for element in self {
try body(element)
}
}
public inline fun
Iterable.forEach(action: (T) -> Unit): Unit {
for (element in this) action(element)
}
inline: ݺͼग़͠ݩʹதΛల։
inline: ݺͼग़͠ݩʹதΛల։
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Some familiar functions
Swift Kotlin
@_inlineable
public func forEach(
_ body: (Element) throws -> Void
) rethrows {
for element in self {
try body(element)
}
}
public inline fun
Iterable.forEach(action: (T) -> Unit): Unit {
for (element in this) action(element)
}
inline: ϩδοΫʹӨڹ͠ͳ͍
inline: ϩδοΫʹӨڹ͢Δ
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Some familiar functions
Swift Kotlin
@_inlineable
public func forEach(
_ body: (Element) throws -> Void
) rethrows {
for element in self {
try body(element)
}
}
public inline fun
Iterable.forEach(action: (T) -> Unit): Unit {
for (element in this) action(element)
}
{
if (it == 2) { return }
println(it)
}
inline: ݺͼग़͠ݩʹதΛల։
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Some familiar functions
Kotlin
listOf(1, 2, 3).forEach {
if (it == 2) { return }
println(it)
}
Iterable $receiver$iv =
(Iterable)CollectionsKt.listOf(new Integer[]
{Integer.valueOf(1), Integer.valueOf(2),
Integer.valueOf(3)});
Iterator var2 = $receiver$iv.iterator();
while(var2.hasNext()) {
Object element$iv = var2.next();
int it = ((Number)element$iv).intValue();
if(it == 2) {
return;
}
System.out.println(it);
}
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Some familiar functions
Kotlin
listOf(1, 2, 3).forEach {
if (it == 2) { return }
println(it)
}
/* ... */
while(var2.hasNext()) {
Object element$iv = var2.next();
int it = ((Number)element$iv).intValue();
if(it == 2) {
return;
}
System.out.println(it);
}
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listOf(1, 2, 3).forEach {
if (it == 2) { return }
println(it)
}
/* ... */
while(var2.hasNext()) {
Object element$iv = var2.next();
int it = ((Number)element$iv).intValue();
if(it == 2) {
return;
}
System.out.println(it);
}
Some familiar functions
Kotlin
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listOf(1, 2, 3).forEach {
if (it == 2) { return }
println(it)
}
/* ... */
while(var2.hasNext()) {
Object element$iv = var2.next();
int it = ((Number)element$iv).intValue();
if(it == 2) {
return;
}
System.out.println(it);
}
Some familiar functions
Kotlin
non-local return
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[1, 2, 3].forEach {
if $0 == 2 { return }
print($0)
}
listOf(1, 2, 3).forEach {
if (it == 2) { return }
println(it)
}
Some familiar functions
Swift Kotlin
1
3
1
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Kotlin
OOP
extension
interface
default
implementati
on
generics
delegation
null
safety
tailrec
static
type
Java
GC
sealed
class
variance
declaration
object
JS
companion
object
if, when
expression
Type
inference
(Corout
ines)
inline
annotation
FP
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Conclusion
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• Started in 2010
• Object-oriented programming
• Support functional programming
• Static typing
• Type inference
• Null safety
• Generic programming
• Some syntax
• Extension
• Default implementation
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&
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Same word, different concept
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Swift ͱ Kotlin
ͲͪΒɺଞͷݴޠ͔ΒػೳࢥΛऔΓೖΕ͍ͯΔ
ͦΕΛͦΕͧΕʹݟ߹ͬͨܗͰ༥߹ͤͭͭ͞ɺ
֤ࣗͷจԽΛங͍͍ͯΔ
ڞ௨͢Δ෦ੜ͡Δ
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enjoy Swift, enjoy Kotlin :)
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References
Kotlin (official reference)
https://kotlinlang.org/docs/reference/
The Swift Programming Language (Swift 4)
https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/AboutTheLanguageReference.html
Programming Kotlin
by Stefan Bocutiu, Stephen Samuel
Swift is like Kotlin: Hacker News (discussion)
https://news.ycombinator.com/item?id=14364612
Swift is like Kotlin
http://nilhcem.com/swift-is-like-kotlin/
SwiftKotlin
https://github.com/angelolloqui/SwiftKotlin
Swift vs Kotlin for real iOS/Android apps (ͱͯྑ͍هࣄͰͨ͠ʂ)
http://angelolloqui.com/blog/38-Swift-vs-Kotlin-for-real-iOS-Android-apps
Swift is NOT like Kotlin..?
http://blog.applibot.co.jp/blog/2017/04/03/swift-is-not-like-kotlin/
iOSΞϓϦ։ൃऀ͔ΒݟͨKotlin (࣌ؒͷ߹Ͱল͍ͨ෦͋Γ·͕͢ɺߏจͷൺֱ͕៉ྷʹ·ͱ·͍ͬͯ·͢)
https://speakerdeck.com/koishi/iosapurikai-fa-zhe-karajian-takotlin
null҆શͰͳ͍ݴޠɺϨΨγʔݴޠͩ (nullable ͷछྨͱಛ)
http://qiita.com/koher/items/e4835bd429b88809ab33#nullable-%E3%81%AE%E7%A8%AE%E9%A1%9E%E3%81%A8%E7%89%B9%E5%BE%B4
Android։ൃΛड͔ͨ͠ΒKotlinΛΨοπϦͬͯΈͨΒ࠷ߴͩͬͨ
http://qiita.com/omochimetaru/items/98e015b0b694dd97f323
͍͠SwiftΤϯδχΞͷͨΊͷKotlinೖ
https://speakerdeck.com/inamiy/mang-siiswiftenziniafalsetamefalsekotlinru-men
Kotlin and Swift. Is it a whole new era in Mobile Development?
https://medium.com/@andycherkashyn/kotlin-and-swift-is-it-a-new-mobile-development-era-b4c5e81feb08
Swift/Kotlin߹ಉษڧձ
https://oi-study.connpass.com/event/62521/
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Q & A
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[1, 2, 3].forEach {
if $0 == 2 { return }
print($0)
}
listOf(1, 2, 3).forEach {
if (it == 2) { return }
println(it)
}
Some familiar functions
Swift Kotlin
1
3
1
࣭
Swift Έ͍ͨͳڍಈʹͰ͖Δʁ
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A: ಗ໊ؔΛ͍·͢
listOf(1, 2, 3).forEach(fun(element: Int) {
if (element == 2) { return }
print(element)
return
}) ͜ͷ return ಗ໊ؔͷ return
͘͢͝ৄ͍͠આ໌
JavaϓϩάϥϚ͕KotlinͰͭ·͖͕ͮͪͳͱ͜Ζ
http://qiita.com/koher/items/
d9411a00986f14683a3f#inline%2d%e3%81%a8%2dnon%2dlocal%2dreturn
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ձͰ͑ͯͩͬͨ͘͞ @omochimetaru ͞Μɺ
هࣄΛࣥචɺπΠʔτ͍͖ͨͩ·ͨ͠ @koher ͞Μ
͋Γ͕ͱ͏͍͟͝·͢ʂ
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Some familiar functions
Swift
@_inlineable
public func first(
where predicate: (Element) throws -> Bool
) rethrows -> Element? {
var foundElement: Element?
do {
try self.forEach {
if try predicate($0) {
foundElement = $0
throw _StopIteration.stop
}
}
} catch is _StopIteration { }
return foundElement
}
ྫ֎͛ͯग़
༨ஊ
Swift Ͱ forEachൈ͚͍ͨͱ͖
ྫ: first(where: )
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࣭
inline ࢦఆΛ͢Δ͜ͱʹΑΔϩδο
ΫޡΓͷճආΛͲ͏͢Δ͔
ճདྷिதʹΞοϓσʔτ͠·͢ʂ
><