Dart 概览

var name = 'Bob';

final a = 3;

var constantList = const [1, 2, 3];
// constantList[1] = 1; // Uncommenting this causes an error.

int.parse('1');
double.parse('1.2');

'a';
"b";
'''
多行字符串1
多行字符串2
'''

var a = 3;
var str = '$a'; // $变量名

var list = [1, 2, 3];
// 数组中只包含某种类型
var names = new List<String>();

var gifts = {
// Keys      Values
  'first' : 'partridge',
  'second': 'turtledoves',
  'fifth' : 'golden rings'
};

gifts['fourth'] = 'calling birds';

// 用泛型
var pages = <String, String>{
  'index.html': 'Homepage',
  'robots.txt': 'Hints for web robots',
  'humans.txt': 'We are people, not machines'
};

返回值 函数名(参数类型：参数名, [可选参数]) {

}

// 可选命名参数
返回值 函数名({参数类型：参数名,参数类型：参数名,}) {

}

bool isNoble(int atomicNumber, [String xx]) {
  return _nobleGases[atomicNumber] != null;
}

=> expr 语法是 { return expr; } 形式的缩写

xxx(3, 4);
xxx(a: 3, b: 4); // 指定参数名创制

import 'dart:io';
import 'package:mylib/mylib.dart'; // 安装的包里找
import 'package:utils/utils.dart';
import 'a.dart'; // 本地找

import 'package:lib1/lib1.dart';
import 'package:lib2/lib2.dart' as lib2;
// ...
Element element1 = new Element();           // Uses Element from lib1.
lib2.Element element2 = new lib2.Element();

// Import only foo.
import 'package:lib1/lib1.dart' show foo;

// Import all names EXCEPT foo.
import 'package:lib2/lib2.dart' hide foo;

library xx;

class Point {
  num x; // 实例变量
  num y;
  num _z; // _ 开头是私有的
  static num d; 静态变量

  // 构造函数
  Point(num x, num y) {
    // There's a better way to do this, stay tuned.
    this.x = x;
    this.y = y;
  }

  // 实例函数
  num distanceTo(Point other) {
    var dx = x - other.x;
    var dy = y - other.y;
    return sqrt(dx * dx + dy * dy);
  }
}

main() {
  var point = new Point();
  point.x = 4;          // Use the setter method for x.
  assert(point.x == 4); // Use the getter method for x.
  assert(point.y == null); // Values default to null.
}

abstract class Doer {
  void doSomething(); // 定义抽象方法。
}

// 实现
class EffectiveDoer extends Doer {
  void doSomething() {
    // ...Provide an implementation, so the method is not abstract here...
  }
}

checkVersion() async {
  var version = await lookUpVersion();
  if (version == expectedVersion) {
    // Do something.
  } else {
    // Do something else.
  }
}