Dart 3 Yenilikleri ve Modern Ozellikler: Eksiksiz Rehber

1// ONCESI (Dart 2): Birden fazla deger dondurmek icin sinif gerekiyordu
2class MinMax {
3  final int min;
4  final int max;
5  MinMax(this.min, this.max);
6}
7 
8MinMax findMinMax(List numbers) {
9  return MinMax(numbers.reduce(min), numbers.reduce(max));
10}
11 
12// SONRASI (Dart 3): Record ile cok daha temiz
13(int min, int max) findMinMax(List numbers) {
14  return (numbers.reduce(min), numbers.reduce(max));
15}
16 
17// Kullanim
18void main() {
19  final result = findMinMax([3, 1, 4, 1, 5, 9, 2, 6]);
20  print('Min: ${result.min}, Max: ${result.max}'); // Adli erisim (named)
21  print('Min: ${result.$1}, Max: ${result.$2}'); // Konumsal erisim (positional)
22}
23 
24// Named records
25({String name, int age, String email}) createUser() {
26  return (name: 'Ahmet', age: 28, email: '[email protected]');
27}
28 
29// Record type alias
30typedef UserRecord = ({String name, int age, String email});
31 
32UserRecord getUser() {
33  return (name: 'Mehmet', age: 32, email: '[email protected]');
34}
35 
36// Record'lar immutable ve value-based equality saglar
37void main() {
38  final a = (1, 'hello');
39  final b = (1, 'hello');
40  print(a == b); // true! (referans degil, deger karsilastirmasi)
41}

1// Temel pattern turleri
2 
3// 1. Variable pattern
4var (x, y) = (10, 20);
5print('x=$x, y=$y'); // x=10, y=20
6 
7// 2. List pattern
8var [a, b, c] = [1, 2, 3];
9print('$a $b $c'); // 1 2 3
10 
11// 3. Map pattern
12var {'name': name, 'age': age} = {'name': 'Ali', 'age': 25};
13print('$name, $age'); // Ali, 25
14 
15// 4. Object pattern
16class Point {
17  final int x;
18  final int y;
19  Point(this.x, this.y);
20}
21 
22void printPoint(Point p) {
23  var Point(x: px, y: py) = p;
24  print('($px, $py)');
25}
26 
27// 5. Rest pattern (...)
28var [first, ...rest, last] = [1, 2, 3, 4, 5];
29print('$first, $rest, $last'); // 1, [2, 3, 4], 5
30 
31// 6. Wildcard pattern (_)
32var (name2, _) = ('Veli', 30); // age'i yoksay
33print(name2); // Veli
34 
35// 7. Guard clause (when)
36String classify(int value) {
37  return switch (value) {
38    int n when n < 0 => 'negatif',
39    0 => 'sifir',
40    int n when n > 0 && n < 100 => 'kucuk pozitif',
41    _ => 'buyuk pozitif',
42  };
43}

1// Dart 3 pattern matching ile JSON parsing
2Map parseApiResponse(Map json) {
3  return switch (json) {
4    {'status': 'success', 'data': Map data} => data,
5    {'status': 'error', 'message': String msg} => throw ApiException(msg),
6    {'status': 'loading'} => throw StateException('Hala yukleniyor'),
7    _ => throw FormatException('Bilinmeyen format'),
8  };
9}
10 
11// Liste icinde pattern matching
12List extractNames(List items) {
13  return [
14    for (final item in items)
15      if (item case {'name': String name, 'active': true})
16        name,
17  ];
18}

1// ONCESI (Dart 2): switch statement
2String getStatusText(Status status) {
3  switch (status) {
4    case Status.idle:
5      return 'Bekliyor';
6    case Status.loading:
7      return 'Yukleniyor';
8    case Status.success:
9      return 'Basarili';
10    case Status.error:
11      return 'Hata';
12  }
13}
14 
15// SONRASI (Dart 3): switch expression
16String getStatusText(Status status) => switch (status) {
17  Status.idle => 'Bekliyor',
18  Status.loading => 'Yukleniyor',
19  Status.success => 'Basarili',
20  Status.error => 'Hata',
21};
22 
23// Widget icinde kullanim
24Widget buildStatusIcon(Status status) => switch (status) {
25  Status.idle => const Icon(Icons.hourglass_empty, color: Colors.grey),
26  Status.loading => const CircularProgressIndicator(),
27  Status.success => const Icon(Icons.check_circle, color: Colors.green),
28  Status.error => const Icon(Icons.error, color: Colors.red),
29};
30 
31// Karmasik pattern'ler ile switch expression
32String describeNumber(num value) => switch (value) {
33  0 => 'sifir',
34  double d when d < 0 => 'negatif ondalik: $d',
35  double d when d > 0 => 'pozitif ondalik: $d',
36  int i when i < 0 => 'negatif tam sayi: $i',
37  int i when i > 0 => 'pozitif tam sayi: $i',
38  _ => 'bilinmiyor',
39};

1// Sealed class tanimi
2sealed class Result {}
3 
4class Success extends Result {
5  final T data;
6  Success(this.data);
7}
8 
9class Loading extends Result {}
10 
11class Error extends Result {
12  final String message;
13  final Exception? exception;
14  Error(this.message, [this.exception]);
15}
16 
17// Exhaustive switch: Tum durumlar ele alinmali!
18// Bir durum eksik kalirsa derleyici HATA verir.
19Widget buildResult(Result result) => switch (result) {
20  Success(data: final user) => Text('Hosgeldin ${user.name}'),
21  Loading() => const CircularProgressIndicator(),
22  Error(message: final msg) => Text('Hata: $msg'),
23  // Yeni bir Result alt tipi eklenirse, derleyici burada uyarir!
24};
25 
26// Gercek dunya ornegi: API durumlari
27sealed class ApiState {
28  const ApiState();
29}
30 
31class ApiInitial extends ApiState {
32  const ApiInitial();
33}
34 
35class ApiLoading extends ApiState {
36  const ApiLoading();
37}
38 
39class ApiSuccess extends ApiState {
40  final T data;
41  const ApiSuccess(this.data);
42}
43 
44class ApiError extends ApiState {
45  final String message;
46  final int? statusCode;
47  const ApiError(this.message, {this.statusCode});
48}
49 
50// Riverpod ile sealed class kullanimi
51class UserNotifier extends Notifier> {
52  @override
53  ApiState build() => const ApiInitial();
54 
55  Future fetchUser(String id) async {
56    state = const ApiLoading();
57    try {
58      final user = await ref.read(userRepositoryProvider).getUser(id);
59      state = ApiSuccess(user);
60    } catch (e) {
61      state = ApiError(e.toString());
62    }
63  }
64}

1// base: Sadece extend edilebilir (implement YAPILAMAZ)
2base class Animal {
3  final String name;
4  Animal(this.name);
5 
6  void makeSound() => print('...');
7}
8 
9// base class Animal'i extend edebilirsin
10class Dog extends Animal {
11  Dog(super.name);
12 
13  @override
14  void makeSound() => print('Hav hav!');
15}
16 
17// AMA implement EDEMEZSIN:
18// class FakeAnimal implements Animal {} // DERLEME HATASI!
19 
20// interface: Sadece implement edilebilir (extend YAPILAMAZ)
21interface class Logger {
22  void log(String message);
23}
24 
25// implement EDEBILIRSIN
26class ConsoleLogger implements Logger {
27  @override
28  void log(String message) => print('[LOG] $message');
29}
30 
31// AMA extend EDEMEZSIN:
32// class SpecialLogger extends Logger {} // DERLEME HATASI!
33 
34// final: Ne extend ne implement edilebilir
35final class DatabaseConfig {
36  final String host;
37  final int port;
38  const DatabaseConfig({required this.host, required this.port});
39}
40 
41// NE extend NE implement:
42// class MyConfig extends DatabaseConfig {} // HATA!
43// class FakeConfig implements DatabaseConfig {} // HATA!
44 
45// mixin class: Hem mixin hem class olarak kullanilabilir
46mixin class Printable {
47  void prettyPrint() => print(toString());
48}
49 
50class User with Printable {
51  final String name;
52  User(this.name);
53 
54  @override
55  String toString() => 'User($name)';
56}

1// If-case: Pattern matching'i if bloklarinda kullanma
2void processResponse(Map json) {
3  // ONCESI
4  if (json.containsKey('data') && json['data'] is Map) {
5    final data = json['data'] as Map;
6    final name = data['name'] as String?;
7    if (name != null) {
8      print('Kullanici: $name');
9    }
10  }
11 
12  // SONRASI (Dart 3)
13  if (json case {'data': {'name': String name}}) {
14    print('Kullanici: $name');
15  }
16}
17 
18// Guard clause ile if-case
19void processAge(Map data) {
20  if (data case {'age': int age} when age >= 18) {
21    print('Yetiskin: $age');
22  } else {
23    print('Gecersiz veya rexit alti');
24  }
25}
26 
27// For dongusu icinde pattern matching
28void processUsers(List> users) {
29  for (final {'name': String name, 'active': bool active} in users) {
30    if (active) {
31      print('Aktif kullanici: $name');
32    }
33  }
34}

1// Record destructuring
2final (lat, lng) = getCoordinates();
3print('Enlem: $lat, Boylam: $lng');
4 
5// List destructuring
6final [first, second, ...rest] = [1, 2, 3, 4, 5];
7print('Ilk: $first, Ikinci: $second, Kalan: $rest');
8 
9// Object destructuring
10final Point(:x, :y) = getOrigin();
11print('x=$x, y=$y');
12 
13// Nested destructuring
14final user = {'name': 'Ayse', 'address': {'city': 'Istanbul', 'zip': '34000'}};
15if (user case {'name': String name, 'address': {'city': String city}}) {
16  print('$name, $city');
17}
18 
19// Swap variables with records
20var (a, b) = (1, 2);
21(a, b) = (b, a); // Degisken takas!
22print('a=$a, b=$b'); // a=2, b=1

1// Dart 3'te null safety kacilamaz!
2// Artik --no-sound-null-safety flagi CALISMAZ.
3 
4// Dogru null handling
5String? getName() => null;
6 
7void main() {
8  final name = getName();
9 
10  // Pattern matching ile null check
11  if (name case String validName) {
12    print('Isim: $validName');
13  } else {
14    print('Isim bos');
15  }
16 
17  // Switch ile null handling
18  final result = switch (name) {
19    String n when n.isNotEmpty => 'Isim: $n',
20    String _ => 'Bos string',
21    null => 'null deger',
22  };
23}

1# 1. Dart versiyonunu guncelle
2# pubspec.yaml'da:
3# environment:
4#   sdk: '>=3.0.0 <4.0.0'
5 
6# 2. Paketleri guncelle
7flutter pub upgrade --major-versions
8 
9# 3. Analiz calistir
10dart analyze
11 
12# 4. Derleme testi
13flutter build apk