FlutterKaigi Day1「Dart のこれから」

Dart のこれから  FlutterKaigi 2022 Day1 

おかやまん / blendthink  株式会社ゆめみ  Android・Flutter テックリード  将棋・プログラミング 

Agenda  01　近年、どのような進化を遂げてきたか   02　Dart の進化プロセス   03　仕様化を進めている新機能   　　・Patterns and
related features   　　・Static Metaprogramming   　　・Views on an object without a wrapper object   　　・Sound declaration-site variance   04　おわりに 

bool isEmpty(String s) => s.length == 0; void main() {
// Runtime error isEmpty(null); } Dart 2.12 - Null safety  bool isEmpty(String s) => s.length == 0; void main() { // Compile-time error isEmpty(null); } 01　近年、どのような進化を遂げてきたか   https://github.com/dart-lang/sdk/blob/main/CHANGELOG.md#2120---2021-03-03  

class A { int x; A(this.x); A.fromString(String s) : x
= int.parse(s); } void main() { final listOfInts = [1, 2, 3]; final listOfStrings = ["1", "2", "3"]; for(final a in listOfInts.map((x) => A(x))) { print(a.x); } for(final a in listOfStrings.map((x) => A.fromString(x))) { print(a.x); } } Dart 2.15 - Constructor tear-offs  class A { int x; A(this.x); A.fromString(String s) : x = int.parse(s); } void main() { final listOfInts = [1, 2, 3]; final listOfStrings = ["1", "2", "3"]; for(final a in listOfInts.map(A.new)) { print(a.x); } for(final a in listOfStrings.map(A.fromString)) { print(a.x); } }  01　近年、どのような進化を遂げてきたか   https://github.com/dart-lang/sdk/blob/main/CHANGELOG.md#2150---2021-12-08  

class A { int x; A(this.x); A.fromString(String s) : x
= int.parse(s); } void main() { final listOfInts = [1, 2, 3]; final listOfStrings = ["1", "2", "3"]; for(final a in listOfInts.map((x) => A(x))) { print(a.x); } for(final a in listOfStrings.map((x) => A.fromString(x))) { print(a.x); } } Dart 2.15 - Constructor tear-offs  class A { int x; A(this.x); A.fromString(String s) : x = int.parse(s); } void main() { final listOfInts = [1, 2, 3]; final listOfStrings = ["1", "2", "3"]; for(final a in listOfInts.map(A.new)) { print(a.x); } for(final a in listOfStrings.map(A.fromString)) { print(a.x); } } 01　近年、どのような進化を遂げてきたか   https://github.com/dart-lang/sdk/blob/main/CHANGELOG.md#2150---2021-12-08  

enum Status { success, failure } extension StatusToCode on Status
{ int get code { switch (this) { case Status.success: return 0; case Status.failure: return 1; } } } Dart 2.17 - Enhanced enums with members  enum Status { success(0), failure(1); final int code; const Status(this.code); } 01　近年、どのような進化を遂げてきたか   https://github.com/dart-lang/sdk/blob/main/CHANGELOG.md#2170---2022-05-11  

class CupertinoPage<T> extends Page<T> { const CupertinoPage({ required this.child, this.maintainState
= true, this.title, this.fullscreenDialog = false, LocalKey? key, String? name, Object? arguments, String? restorationId, }) : super( key: key, name: name, arguments: arguments, restorationId: restorationId, ); // ... } Dart 2.17 - Super parameters  class CupertinoPage<T> extends Page<T> { const CupertinoPage({ required this.child, this.maintainState = true, this.title, this.fullscreenDialog = false, super.key, super.name, super.arguments, super.restorationId, }); // ... } 01　近年、どのような進化を遂げてきたか   https://github.com/dart-lang/sdk/blob/main/CHANGELOG.md#2170---2022-05-11  

main() { test('A test description', () { // Very long
function body here... }, skip: true); } Dart 2.17 - Named args everywhere  main() { test(skip: true, 'A test description', () { // Very long function body here... }); } 01　近年、どのような進化を遂げてきたか   https://github.com/dart-lang/sdk/blob/main/CHANGELOG.md#2170---2022-05-11  

• Dart 2.18  ◦ Enhanced type inference for generic invocations
with function literals   • Dart 2.17  ◦ Enhanced enums with members  ◦ Super parameters  ◦ Named args everywhere  • Dart 2.15  ◦ Constructor tear-offs  ◦ Generic type literals  ◦ Explicit generic method instantiations  ◦ Generic instantiation of function objects  • Dart 2.14  ◦ Unsigned shift operator  ◦ Removed some restrictions on type arguments  • Dart 2.13  ◦ Non-function type aliases  • Dart 2.12  ◦ Null safety  01　近年、どのような進化を遂げてきたか   https://github.com/dart-lang/sdk/blob/main/CHANGELOG.md  

Dart の言語チーム  ※ 2020 年 6 月時点   leafpetersen  
lrhn  eernstg  munificent  natebosch  jakemac53  stereotype441   mit-mit  02　Dart の進化プロセス   https://github.com/dart-lang/language/blob/master/README.md#dart-language-team  

機能が追加されるまでの流れ    02　Dart の進化プロセス   https://github.com/dart-lang/language/blob/master/doc/life_of_a_language_feature.md  

機能が追加されるまでの流れ  02　Dart の進化プロセス   https://github.com/dart-lang/language/issues/2534  

機能が追加されるまでの流れ  02　Dart の進化プロセス   https://github.com/dart-lang/language/issues/2558  

機能が追加されるまでの流れ  02　Dart の進化プロセス   https://github.com/dart-lang/language/projects/1  

機能が追加されるまでの流れ  02　Dart の進化プロセス   ※ 2022 年 10 月時点  
https://github.com/dart-lang/language/projects/1  

機能が追加されるまでの流れ  02　Dart の進化プロセス   https://github.com/dart-lang/language/projects/1   https://github.com/dart-lang/language/blob/master/working/macros/feature-specification.md  

機能が追加されるまでの流れ  02　Dart の進化プロセス   https://github.com/dart-lang/language/blob/master/accepted/2.14/triple-shift-operator/implementation-plan.md   https://github.com/dart-lang/language/blob/master/accepted/2.14/triple-shift-operator/feature-specification.md   https://github.com/dart-lang/language/issues/478  

機能が追加されるまでの流れ  02　Dart の進化プロセス  

Patterns and related features  03　仕様化を進めている新機能 - Patterns and related features
  https://github.com/dart-lang/language/projects/1  

Patterns and related features  03　仕様化を進めている新機能 - Patterns and related features
  https://github.com/dart-lang/language/issues/546  

コンセプト  • パターン  • パターンマッチング  • 網羅性  • 分割代入  •
タプル  • 代数的データ型  • データクラス  03　仕様化を進めている新機能 - Patterns and related features  

Record 機能 - 提案の動機  03　仕様化を進めている新機能 - Patterns and related features
  Future<String> getPersonName() async => 'John'; Future<int> getUnreadCount() async => 10; void main() async { // List<Object> final result = await Future.wait([ getPersonName(), getUnreadCount(), ]); final personName = result[0] as String; final unreadCount = result[1] as int; final lowOrHigh = unreadCount < 10 ? 'low' : 'high'; // John's unread count is high. print("$personName’s unread count is $lowOrHigh."); }

Record 機能 - 提案の動機  03　仕様化を進めている新機能 - Patterns and related features
  Future<String> getPersonName() async => 'John'; Future<int> getUnreadCount() async => 10; void main() async { // List<Object> final result = await Future.wait([ getPersonName(), getUnreadCount(), ]); final personName = result[0] as String; final unreadCount = result[1] as int; final lowOrHigh = unreadCount < 10 ? 'low' : 'high'; // John's unread count is high. print("$personName's unread count is $lowOrHigh."); }

Record 機能 - 概要  03　仕様化を進めている新機能 - Patterns and related features
  var tuple = ("first", 2, true);  var record = (number: 123, name: "Main", type: "Street"); var record = ("first", number: 123, 2, name: "Main", true, type: "Street");

Record 機能 - 概要  03　仕様化を進めている新機能 - Patterns and related features
  var record = (1, a: 2, 3, b: 4); print(record.$0); // Prints "1". print(record.a); // Prints "2". print(record.$1); // Prints "3". print(record.b); // Prints "4".

Record 機能 - 注釈  03　仕様化を進めている新機能 - Patterns and related features
  (int, String name, bool) triple; ({int n, String s}) pair; (bool, num, {int n, String s}) quad;

  @metadata (a, b) function() {} 

Record 機能 - toString()  03　仕様化を進めている新機能 - Patterns and related features
  // デバッグビルド print((1, 2, 3).toString()); // "(1, 2, 3)". print((a: 'str', 'int').toString()); // "(a: str, int)".

Record 機能 - 等価性  03　仕様化を進めている新機能 - Patterns and related features
  var a = (x: 1, 2); var b = (2, x: 1); print(a == b); // true.

Record 機能 - with()  03　仕様化を進めている新機能 - Patterns and related features
  void main() { (int, int, {Color color}) x = (0, 1, color: Color.red); var x2 = x.with(7); // Just changes x[0]. var x3 = x.with(_, 3); // Just changes x[1]. var x4 = x.with(1: 3); // Also just changes x[1]. var x5 = x.with(color: Color.Blue); // Just changes x.color. }

Pattern 機能 - 提案の動機  03　仕様化を進めている新機能 - Patterns and related features
  void main() async { try { await fetchData(); } on SocketException { handleException(); } on TimeoutException { handleException(); } }

Pattern 機能 - 提案の動機  03　仕様化を進めている新機能 - Patterns and related features
  void main() async { try { await fetchData(); } on SocketException, TimeoutException { handleException(); } }

Pattern 機能 - 概要  03　仕様化を進めている新機能 - Patterns and related features
  パターンに関する基本的な考え方  • パターンが値と一致するかどうかを判断するために、ある値に対してテストすることができる  • いくつかのパターンは、マッチした場合、マッチした値からデータを取り出すことによって、マッチした値を再構築する  • 変数パターンは、マッチした値または非構造化された値に新しい変数をバインドする。変数は、パターンがマッチしたときにのみ到達可能なコード領域内にスコープされる 

Pattern 機能 - 概要  03　仕様化を進めている新機能 - Patterns and related features
  種類例論理和 subpattern1 | subpattern2 論理積 subpattern1 & subpattern2 関連 == expression, < expression キャスト foo as String null チェック subpattern? null アサート subpattern! 定数 123, null, 'string', math.pi, SomeClass.constant, const Thing(1, 2), const (1 + 2) 変数 foo, var bar, String str, _, int _ 括弧付き (subpattern) List [subpattern1, subpattern2] Map {"key": subpattern1, someConst: subpattern2} Record (subpattern1, subpattern2), (x: subpattern1, y: subpattern2) 抽出 SomeClass(x: subpattern1, y: subpattern2) https://github.com/dart-lang/language/blob/master/working/0546-patterns/patterns-feature-specification.md  

Pattern 機能 - 論理和パターン  03　仕様化を進めている新機能 - Patterns and related features
  var isPrimary = switch (color) { case Color.red | Color.yellow | Color.blue => true; default => false; };

  switch (shape) { case Square(size: var s) | Circle(size: var s) when s > 0: print('Non-empty symmetric shape'); case Square() | Circle(): print('Empty symmetric shape'); default: print('Asymmetric shape'); }

  switch (list) { // Matches a two-element list whose first element is 'a' or 'b': case ['a' | 'b', var c]: }

網羅性チェック - 概要  03　仕様化を進めている新機能 - Patterns and related features  
• 網羅性      • 到達可能性  switch (b) { case true: print('yes'); case false: print('no'); }  switch (b) { case true: print('yes'); case false: print('no'); case bool b: print('unreachable'); } 

Static Metaprogramming  03　仕様化を進めている新機能 - Static Metaprogramming   https://github.com/dart-lang/language/projects/1  

Static Metaprogramming  03　仕様化を進めている新機能 - Static Metaprogramming   https://github.com/dart-lang/language/issues/1482  

マクロ - 提案の動機  03　仕様化を進めている新機能 - Static Metaprogramming   data class
User(val name: String, val age: Int) 

マクロ - 提案の動機  03　仕様化を進めている新機能 - Static Metaprogramming   @immutable class
User { const User({ required this.name, required this.age, }); final String name; final int age; @override bool operator ==(Object other) => other is User && other.runtimeType == runtimeType && other.name == name && other.age == age; @override int get hashCode => Object.hash( runtimeType, name, age, ); @override String toString() => 'User(' 'name=$name, ' 'age=$age' ')'; User copy({ String? name, int? age, }) => User( name: name ?? this.name, age: age ?? this.age, ); }

マクロ - 提案の動機  03　仕様化を進めている新機能 - Static Metaprogramming   import 'package:freezed_annotation/freezed_annotation.dart';
part 'user.freezed.dart'; @freezed class User with _$User { const factory User({ required String name, required int age, }) = _User; }

マクロ - 概要  03　仕様化を進めている新機能 - Static Metaprogramming   macro class
DataClass implements ClassDeclarationsMacro, ClassDefinitionMacro { const DataClass(); @override Future<void> buildDeclarationsForClass( ClassDeclaration clazz, ClassMemberDeclarationBuilder context) async { await Future.wait([ const AutoConstructor().buildDeclarationsForClass(clazz, context), const CopyWith().buildDeclarationsForClass(clazz, context), const HashCode().buildDeclarationsForClass(clazz, context), const Equality().buildDeclarationsForClass(clazz, context), const ToString().buildDeclarationsForClass(clazz, context), ]); } @override Future<void> buildDefinitionForClass( ClassDeclaration clazz, ClassDefinitionBuilder builder) async { await Future.wait([ const HashCode().buildDefinitionForClass(clazz, builder), const Equality().buildDefinitionForClass(clazz, builder), const ToString().buildDefinitionForClass(clazz, builder), ]); } }

マクロ - 概要  03　仕様化を進めている新機能 - Static Metaprogramming   https://github.com/dart-lang/sdk/tree/main/pkg/_fe_analyzer_shared/lib/src/macros  

マクロ - 概要  03　仕様化を進めている新機能 - Static Metaprogramming   https://github.com/dart-lang/language/tree/master/working/macros/example  

Views on an object without a wrapper object  03　仕様化を進めている新機能 -
Views on an object without a wrapper object   https://github.com/dart-lang/language/projects/1  

Views on an object without a wrapper object  03　仕様化を進めている新機能 -
Views on an object without a wrapper object   https://github.com/dart-lang/language/issues/1474  

View - 提案の動機  03　仕様化を進めている新機能 - Views on an object without
a wrapper object   • 拡張メソッドのように、ラッパーオブジェクトなしで、ゼロコストで特定のオブジェクトを拡張したい  • ラッピングすることで、不適切な操作を禁止したり、回帰的な処理をより便利かつ安全に実装したりしたい 

View - 概要  03　仕様化を進めている新機能 - Views on an object without
a wrapper object   view class IdNumber(int i) { operator <(IdNumber other) => i < other.i; bool verify(Some parameters) => ...; }

View - 概要  03　仕様化を進めている新機能 - Views on an object without
a wrapper object   view class IdNumber(int i) { operator <(IdNumber other) => i < other.i; bool verify(Some parameters) => ...; } void main() { int myUnsafeId = 42424242; var safeId = IdNumber(42424242); safeId + 10; // Compile-time error 10 + safeId; // Compile-time error myUnsafeId = safeId; // Compile-time error }

Sound declaration-site variance  03　仕様化を進めている新機能 - Sound declaration-site variance   https://github.com/dart-lang/language/projects/1
 

Sound declaration-site variance  03　仕様化を進めている新機能 - Sound declaration-site variance   https://github.com/dart-lang/language/issues/524
 

提案の動機  03　仕様化を進めている新機能 - Sound declaration-site variance   class Writer<T> {
void write(T x) => print(x); } void main() { Writer<Object> objectWriter = Writer<int>(); // Runtime error objectWriter.write("I'm a string!"); }

概要  03　仕様化を進めている新機能 - Sound declaration-site variance   class Writer<in T>
{ void write(T x) => print(x); } void main() { // Compile-time error Writer<Object> objectWriter = Writer<int>(); objectWriter.write("I'm a string!"); }

概要  03　仕様化を進めている新機能 - Sound declaration-site variance   https://github.com/dart-lang/language/pull/557  

Dart の進化を支えている  言語チームメンバーに感謝！ 

ご清聴ありがとうございました 

FlutterKaigi Day1「Dart のこれから」

FlutterKaigi Day1「Dart のこれから」

Transcript

More Decks by おかやまん

Other Decks in Technology

Featured