ActionScript 3.0 Notes (4) - Type

Type

²       General

e.g.

(1) ActionScript 3.0 引入了无类型变量(undefined)这一概念

var someObj:*;

var someObj;

(2) 在 ActionScript 3.0 中，出于实用的目的，不对基元值及其包装对象加以区分。所有的值（甚至基元值）都是对象。但运行时基元视为特例，它们不需要创建对象所涉及的正常开销。So下面的两行代码是等效的：

var someInt:int = 3;

var someInt:int = new int(3);

var someArray:Array = [1, 2, 3]; // literal value

var numArray:Array = ["zero", "one", "two"];

var someArray:Array = new Array(1,2,3); // Array constructor

(3) type conversion (类型转换): var myINT:int = int(myBoolean);

 

typeof

 

²       var / const / get set

三种方法来声明属性：

用 const 关键字定义常量，用 var 关键字定义变量，用 get 和 set 属性定义 getter 和 setter 属性;

可以对从超类继承的 getter 和 setter 函数使用 override 属性。

getter / setter e.g.

public function get publicAccess():String     { return privateProperty; }     public function set publicAccess(setValue:String):void     { privateProperty = setValue; }

 

²       Boolean / Number / String / *

default of type

Type	Default	Type	Default
Boolean	false	int	0
Number	NaN	uint	0
String	null	Object	null
(not declare) / *	undefined	(other)	null

Note:

(1) 应将 Number 数据类型仅用于浮点数，或者用于大于32位的整数值。如果您尝试计算负数的平方根，结果会是 NaN。

(2) String 在内部存储为 Unicode 字符，并使用 UTF-16 格式。null 与空字符串 ("") 不同。值 null 表示变量中未存储任何值，而空串表示变量中有一个 String 值，但其中不包含任何字符。

 

²       other type

Array, Date, Error, Function, RegExp, XML, XMLList …

Day, Timer,

 

²       Array

General

Sort: reverse(), sort(), sortOn()

concat() , join() , slice() , toString()

var oddNumbers:Array = [1, 3, 5, 7, 9, 11]; var len:uint = oddNumbers.length; for (var i:uint = 0; i < len; i++) { ...   var names:Array = new Array(3); trace(names.length); // output: 3 trace(names[0]); // output: undefined   var names:Array = new Array("John", "Jane", "David"); var names:Array = ["John", "Jane", "David"];   var planets:Array = new Array(); planets.push("Mars"); // array contents: Mars planets.unshift("Mercury"); // array contents: Mercury,Mars planets.splice(1, 0, "Venus", "Earth"); trace(planets); // array contents: Mercury,Venus,Earth,Mars

indexed array: key int, reference with [],  Associative array: key String/Object, reference with [“”] dot(.) / []

 

Associative arrays (关联数组)

也称为”哈希”或”映射”，由key和value组成的无序集合。

var monitorInfo:Object = {type:"Flat Panel", resolution:"1600 x 1200"};  // 1st way, generic object trace(monitorInfo["type"], monitorInfo["resolution"]);  // output: Flat Panel 1600 x 1200   var monitorInfo:Object = new Object();  // 2nd way, Object constructor monitorInfo["aspect ratio"] = "16:10";  // Using spaces in your key names is not recommended monitorInfo.colors = "16.7 million"; trace(monitorInfo["aspect ratio"], monitorInfo.colors);  // output: 16:10 16.7 million

 

Associative arrays with object keys (Dictionaries)

You can use the Dictionary class to create an associative array that uses objects for keys rather than strings.

import flash.utils.Dictionary; var groupMap:Dictionary = new Dictionary();   // objects to use as keys var spr1:Sprite = new Sprite();   // objects to use as values var groupA:Object = new Object();   // Create new key-value pairs in dictionary. groupMap[spr1] = groupA;   for (var key:Object in groupMap) {   trace(key, groupMap[key]);  // output: [object Sprite] [object Object] }

 

Multidimensional arrays (多维数组)

var masterTaskList:Array = new Array(); masterTaskList[0] = ["wash dishes", "take out trash"]; masterTaskList[1] = ["wash dishes"]; trace(masterTaskList[0][1]); // output: take out trash   /* Associative array with an indexed array */ var masterTaskList:Object = new Object(); masterTaskList["Monday"] = ["wash dishes", "take out trash"]; masterTaskList["Sunday"] = ["mow lawn", "fix chair"]; trace(masterTaskList.Sunday[0]);// output: mow lawn

 

Cloning arrays

1. shallow copy

(references to the objects are copied)

calling either the concat() or slice() methods with no arguments

 

2. deep copy

(new array does not point to the same objects)

// The algorithm is borrowed from a common Java programming technique function clone(source:Object):* {     var myBA:ByteArray = new ByteArray();     myBA.writeObject(source);     ...     return(myBA.readObject());

 

extends / override arrays

Detail: http://help.adobe.com/en_US/ActionScript/3.0_ProgrammingAS3/WS5b3ccc516d4fbf351e63e3d118a9b90204-7ee4.html

 

Detail: http://help.adobe.com/zh_CN/as3/learn/WSf00ab63af761f1702761490412937d6fc9b-7ff5.html

 

²       Vector.<T>()

Unlike with the Array class, you can’t pass a list of values to the Vector.<T>() constructor to specify the Vector’s initial values.

var ages:Vector.<uint> = new Vector.<uint>(3);  // using constructor trace(ages); // output: 0,0,0   var numbers:Vector.<int> = Vector.<int>(["1.5", "17", "Waffles"]);  // using global function trace(numbers); // output: 1,17,0  non-numeric value is converted to 0

Note: The Vector class is available starting with Flash Player 10 and Adobe AIR 1.5.