Dart语言

Thu, 05 Feb 2026 00:00:00 +0000

Dart

主函数

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void main(){
 print('Hello World!');
}

变量

var

Object, String(?), late, final(const)

流程控制语句

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if (year >= 2001) {
 print('21st century');
} else if (year >= 1901) {
 print('20th century');
}

for (final object in flybyObjects) {
 print(object);
}

for (int month = 1; month <= 12; month++) {
 print(month);
}

while (year < 2016) {
 year += 1;
}

函数

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int fibonacci(int n) {
 if (n == 0 || n == 1) return n;
 return fibonacci(n - 1) + fibonacci(n - 2);
}

var result = fibonacci(20);

类

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class Spacecraft {
 String name;
 DateTime? launchDate;

 // Read-only non-final property
 int? get launchYear => launchDate?.year;

 // Constructor, with syntactic sugar for assignment to members.
 Spacecraft(this.name, this.launchDate) {
 // Initialization code goes here.
 }

 // Named constructor that forwards to the default one.
 Spacecraft.unlaunched(String name) : this(name, null);

 // Method.
 void describe() {
 print('Spacecraft: $name');
 // Type promotion doesn't work on getters.
 var launchDate = this.launchDate;
 if (launchDate != null) {
 int years = DateTime.now().difference(launchDate).inDays ~/ 365;
 print('Launched: $launchYear ($years years ago)');
 } else {
 print('Unlaunched');
 }
 }
}

// 使用类
var voyager = Spacecraft('Voyager I', DateTime(1977, 9, 5));
voyager.describe();

var voyager3 = Spacecraft.unlaunched('Voyager III');
voyager3.describe();

其他

=> (胖箭头)

简写语法用于仅包含一条语句的函数：

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flybyObjects.where((name) => name.contains('turn')).forEach(print);

注释(comments)

//
/* … */
///(Documentation)

枚举

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enum PlanetType { terrestrial, gas, ice }

继承

支持单继承

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class Orbiter extends Spacecraft {
 double altitude;

 Orbiter(super.name, DateTime super.launchDate, this.altitude);
}

Mixin

一种在多个类层次结构中重用代码的方法

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mixin Piloted {
 int astronauts = 1;

 void describeCrew() {
 print('Number of astronauts: $astronauts');
 }
}

class PilotedCraft extends Spacecraft with Piloted {
 // ···
}

接口和抽象类

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class MockSpaceship implements Spacecraft {
 // ···
}

abstract class Describable {
 void describe();

 void describeWithEmphasis() {
 print('=========');
 describe();
 print('=========');
 }
}

异步

使用 async 和 await 关键字可以让你避免回调地狱 (Callback Hell) 并使你的代码更具可读性。

异常

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Future<void> describeFlybyObjects(List<String> flybyObjects) async {
 try {
 for (final object in flybyObjects) {
 var description = await File('$object.txt').readAsString();
 print(description);
 }
 } on IOException catch (e) {
 print('Could not describe object: $e');
 } finally {
 flybyObjects.clear();
 }
}

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import 'dart:convert';
import 'package:http/http.dart' as http;

class Package {
 final String name;
 final String latestVersion; 
 final String? description;

 Package(this.name, this.latestVersion, {this.description});

 @override
 String toString() {
 return 'Package{name: $name, latestVersion: $latestVersion, description: $description}';
 }
}

void main() async {
 final httpPackageUrl = Uri.https('dart.dev', '/f/packages/http.json');
 final httpPackageResponse = await http.get(httpPackageUrl);
 if (httpPackageResponse.statusCode != 200) {
 print('Failed to retrieve the http package!');
 return;
 }
 final json = jsonDecode(httpPackageResponse.body);
 final package = Package(
 json['name'],
 json['latestVersion'],
 description: json['description'],
 );
 print(package);
}

计算机语言 on ༺KO༒NE༻

Dart语言

Dart

主函数

变量

流程控制语句

函数

类

其他

=> (胖箭头)

注释(comments)

枚举

继承

Mixin

接口和抽象类

异步

异常