AS3: How to convert a Vector to an Array

问题:

What's the nicest way to convert a Vector to an Array in Actionscript3?

The normal casting syntax doesn't work:

var myVector:Vector. = new Vector(); var myArray:Array = Array(myVector); // calls the top-level function Array() 

due to the existance of the Array function. The above results in an array, but it's an array with a single element consisting of the original Vector.

Which leaves the slightly more verbose:

var myArray:Array = new Array(); for each (var elem:Foo in myVector) {     myArray.push(elem); } 

which is fine, I guess, though a bit wordy. Is this the canonical way to do it, or is there a toArray() function hiding somewhere in the standard library?

回答1:

your approach is the fastest ... if you think it's to verbose, then build a utility function ... :)

edit:

To build a utility function, you will probably have to drop the type as follows:

function toArray(iterable:*):Array {      var ret:Array = [];      for each (var elem:Foo in iterable) ret.push(elem);      return ret; } 

回答2:

There is a function called forEach which both Vector and Array has which you can use. Basically it calls a function for each element in the vector. This is how it works:

var myVector:Vector. = new Vector(); var myArray:Array = [];  myVector.forEach(arrayConverter);  function arrayConverter(element:*, index:int, array:Array):void{     myArray[myArray.length] = element; } 

But I couldn't find a function which just moves all the values from the Vector to an Array. Another solution could be that you create a class which extends the Vector class and then you have a public function called toArray() and then you have that code in that function so you don't have to write it each time you want to convert.

Vector documentation

Edit: Found this old question today and thought it would be interesting to do a benchmark test of all the different methods this sunday morning.

I used a vector with 1000000 items in and made 2 tests for each loop. One using the built in array functions push and one using regular array operations.

• For loop, not push: 520 ms
• For loop, push: 1027 ms
• Foreach loop, not push: 1753 ms
• Foreach loop, push: 2264 ms
• While loop, not push: 2775 ms
• While loop, not push: 3282 ms
• Util loop, not push: 4059 ms
• Util loop, push: 4570 ms

And here is a benchmark using 1000 items:

• For loop, not push: 1 ms
• For loop, push: 2 ms
• Foreach loop, not push: 2 ms
• Foreach loop, push: 3 ms
• While loop, not push: 3 ms
• While loop, not push: 4 ms
• Util loop, not push: 4 ms
• Util loop, push: 5 ms

Basically it's when you get over 10 000 items you start to see the real difference. So between 0 and 10 000 items it doesn't really matter which you use.

package {     public class Loops{         public static function forLoop(vector:Vector., usePush:Boolean = false):Array{             var result:Array = [];              for(var i:int = 0; i , usePush:Boolean):Array{             var result:Array = [];              for each(var key:String in vector){                 if(usePush){                     result.push(vector[key]);                 }else{                     result[result.length] = vector[key];                 }             }              return result;                   }          public static function whileLoop(vector:Vector., usePush:Boolean):Array{             var result:Array = [];              var i:int = 0;             while(i , usePush:Boolean):Array{             var result:Array = [];              function arrayUtilForeach(element:*, index:int, array:Array):void{                 if(usePush){                     array.push(element);                 }else{                     array[result.length] = element;                 }             }                         vector.forEach(arrayUtilForeach);              return result;                   }     } } 

I used the getTimer function to do the benchmark, so it might not be 100% accurate but there's so much difference between the different loops so I don't think it matters.

I hope someone found this useful.

回答3:

use:

var myArray:Array = []; myArray.push.apply(null, myVector); 

or

var myArray:Array = new Array().concat(myVector); 

回答4:

for each will not guarantee that the order of your items will be the same.
for in should give you a closer match.

    private var _vector:*;      public function VectorUtil(vector:*)     {         _vector = vector;     }      public function toArray():Array     {         var a:Array = [];         for (var i:int = 0; i 

回答5:

Vaukalak second answer not only works but is much faster than the top voted answer here, I've massaged it a little as [] produces fractionally faster array construction than new Array(). Also included below is the best way to create a Vector from an Array too.

// make a Vector from an array var toVector : Vector. = Vector.(['a','b','c'])   // populate an array from a Vector var toArray : Array = [].concat(toVector); 

Please note, this only seems to work with flash 11

回答6:

a function call for each element in the Vector would be a LOT slower, particularly in a longer Vector. however, these examples are probably all equivalent, unless you're dealing with a fairly long Vector/Array -- legibility and ease of use are generally more important than optimization.

that said, i think the fastest way is to use a while loop with an iterator compared against 0.

var myArray:Array = new Array(myVector.length); var i:int=myVector.length; while (i--) {     myArray[i] = myVector[i]; } 

unfortunately, you can't stuff this technique into a method for ease of repeated use, because there's no way to specify a Vector method parameter of a generic base type.... :(

回答7:

If you have a vector of strings, you could do:

myArray = myVec.join(",").split(","); 

for a quick and dirty Array conversion.

回答8:

var a:Array = some_vector as Array;

文章来源: AS3: How to convert a Vector to an Array