免责声明：本文档基本是官网文档的摘抄和简单翻译，几乎没有任何原创。
本文是我本人对Dart学习所做的笔记，目的是记录和整理。
Dart里的一些显著不同于其他编程语言的语法整理。
Dart具有多种编程范式，这点和C++相同，不强制面向对象。然而在各种语法上更接近Java和C#，除了没有public、protected、private之类的修饰关键字。
下面的东西为我个人笔记，无意做教程，所以写的比较乱。不过反正也应该没什么人看。
1.构造函数：初始化成员变量的语法糖
class Point {
num x, y;
// Syntactic sugar for setting x and y
// before the constructor body runs.
Point(this.x, this.y);
}
2.Named constructors(命名构造函数)
class Point {
num x, y;
Point(this.x, this.y);
// Named constructor
Point.origin() {
x = 0;
y = 0;
}
}
3.调用父类非默认的构造函数（默认构造函数应该就是无参构造函数）
class Person {
String firstName;
Person.fromJson(Map data) {
print('in Person');
}
}
class Employee extends Person {
// Person does not have a default constructor;
// you must call super.fromJson(data).
Employee.fromJson(Map data) : super.fromJson(data) {
print('in Employee');
}
}
或者只初始化父类构造函数就结束，无需写{}，直接加分号结束
class Employee extends Person {
Employee() : super.fromJson(getDefaultData());
// ···
}
4.初始化列表
class Point {
final num x;
final num y;
final num distanceFromOrigin;
Point(x, y)
: x = x,
y = y,
distanceFromOrigin = sqrt(x * x + y * y);
// Initializer list sets instance variables before
// the constructor body runs.
Point.fromJson(Map json)
: x = json['x'],
y = json['y'] {
print('In Point.fromJson(): ($x, $y)');
}
}
- getter ,setter
class Rectangle {
num left, top, width, height;
Rectangle(this.left, this.top, this.width, this.height);
// Define two calculated properties: right and bottom.
num get right => left + width;
set right(num value) => left = value - width;
num get bottom => top + height;
set bottom(num value) => top = value - height;
}
6.隐式接口
每个类隐式地声明了一个接口，此接口的成员包括这个类所有的实例成员及它所实现接口的函数。
如果类A想要实现类B的API，并且不继承类B的任何实现方式，只需要通过implements关键字来实现B即可，而不是extends。
这说明Dart不使用interface关键字来声明接口，而每个类都是接口，只要被其他类implements。
// A person. The implicit interface contains greet().
class Person {
// In the interface, but visible only in this library.
final _name;
// Not in the interface, since this is a constructor.
Person(this._name);
// In the interface.
String greet(String who) => 'Hello, $who. I am $_name.';
}
// An implementation of the Person interface.
class Impostor implements Person {
get _name => '';
String greet(String who) => 'Hi $who. Do you know who I am?';
}
7.运算符重载，基本和C++相同
class Vector {
final int x, y;
Vector(this.x, this.y);
Vector operator +(Vector v) => Vector(x + v.x, y + v.y);
Vector operator -(Vector v) => Vector(x - v.x, y - v.y);
// Operator == and hashCode not shown. For details, see note below.
// ···
}
8.继承，枚举，泛型基本和Java相同
区别在于dart的泛型有简写语法糖
var names = ['Seth', 'Kathy', 'Lars'];
var uniqueNames = {'Seth', 'Kathy', 'Lars'};
var pages = {
'index.html': 'Homepage',
'robots.txt': 'Hints for web robots',
'humans.txt': 'We are people, not machines'
};
9.引入第三方库
可以使用路径引入本地库。
dart开头的库是dart自带的标准库。
package开头的库需要在 package manager 里，比如pub tool。
import 'dart:html';
import 'package:test/test.dart';
import 'package:lib1/lib1.dart';
import 'package:lib2/lib2.dart' as lib2; //避免引入重名类，可以使用标识
// Import only foo.
import 'package:lib1/lib1.dart' show foo;
// Import all names EXCEPT foo.
import 'package:lib2/lib2.dart' hide foo;
10.支持aynsc/await
Future checkVersion() async {
var version = await lookUpVersion();
// Do something with version
}
Future lookUpVersion() async => '1.0.0';
11.streams
可以直接使用for循环处理异步数据流
Future main() async {
// ...
await for (var request in requestServer) {
handleRequest(request);
}
// ...
}
- Generators，生成器
和python基本相同
注意声明后边的sync*和async*,导致了返回值的不同，分别返回了Iterable和Stream。
Iterable naturalsTo(int n) sync* {
int k = 0;
while (k < n) yield k++;
}
Stream asynchronousNaturalsTo(int n) async* {
int k = 0;
while (k < n) yield k++;
}
13.可调用的类（函子）（Callable classes）
class WannabeFunction {
call(String a, String b, String c) => '$a $b $c!';
}
main() {
var wf = new WannabeFunction();
var out = wf("Hi","there,","gang");
print('$out');
}
- Isolates 类似于线程
dart:isolate library documentation.
15.typedef
与C++基本相同
typedef Compare = int Function(Object a, Object b);
class SortedCollection {
Compare compare;
SortedCollection(this.compare);
}
int sort(Object a, Object b) => 0;
void main() {
SortedCollection coll = SortedCollection(sort);
}
16.元数据注解(Metadata)
library todo;
class Todo {
final String who;
final String what;
const Todo(this.who, this.what);
}
//===========
import 'todo.dart';
@Todo('seth', 'make this do something')
void doSomething() {
print('do something');
}