Re: [flexcoders] any performance hit using "as"?

Tue, 08 Aug 2006 09:40:37 -0700

Hi Ted,
maybe i misunderstand you,
but your example works like expected for me.

myArray = aCollection as Array;

Since aCollection is not an Array, myArray is null afterwards.

Cheers,
Ralf.


On 8/8/06, Ralf Bokelberg < [EMAIL PROTECTED]> wrote:
Huh,
i'd expect that myArray is null, because aCollection is not an Array.
Cheers,
Ralf.


On 8/8/06, Ted Patrick < [EMAIL PROTECTED]> wrote:

Using 'as' can get confusing as it has a subtle gotcha. 'as' will return the object if it inherits from the target Class else it returns null.

 

This is great behavior until you try it with Classes that inherit from Proxy.

 

Example: myVar will be null, 100% of the time!!!

 

var aCollection:ArrayCollection;

var myArray:Array;

 

aCollection = new ArrayCollection( [1,2,3] );

myArray = aCollection as Array;

 

ArrayCollection does not inherit from Array, it holds an array internally and uses Proxy to provide an alternative interface.

 

Cheers,

 

Ted Patrick

Flex Evangelist

Adobe Systems Incorporated

 

 

From: [email protected] [mailto:[email protected]] On Behalf Of Pan Troglodytes
Sent: Tuesday, August 08, 2006 8:11 AM
To: [email protected]
Subject: Re: [flexcoders] any performance hit using "as"?

 

Thanks for the reply, Matt.  Is there any performance difference between all three?  I'm curious if doing any casting at all is a performance hit.

On 8/7/06, Matt Chotin < [EMAIL PROTECTED]> wrote:

I don't think there should be a performance difference between the two.

 

Matt

 

From: [email protected] [mailto:[email protected]] On Behalf Of Pan Troglodytes
Sent: Monday, August 07, 2006 9:21 AM
To: flexcoders
Subject: [flexcoders] any performance hit using "as"?

 

I tend to like to make my code autosense for me, so sometimes I do things like this:

MyObjectType(grid.selectedItem).somefield = 3;

I assume that adds no overhead, since it is a straight cast (though I could be wrong), since I have seen runtime errors specifically telling me my cast was wrong.  But sometimes with Array, I have to use "as" because it gets a cast confused with a new array contructor.  So I'm wondering what the difference in performance is, if any.

Given then grid.selectedItem is MyObjectType, consider the following statements:

grid.selectedItem.somefield = 3;
MyObjectType(grid.selectedItem).somefield = 3;
(grid.selectedItem as MyObjectType).somefield = 3;


Is there any runtime performance difference to them?  I only just now read the help on "as" I noticed that if it is NOT the desired type, it returns null.  That totally messes with my brain, coming from a Delphi background where as throws an exception if it is not the right type.  But the thrust of my question involves them being the desired type.

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Jason




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Jason




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Ralf Bokelberg < [EMAIL PROTECTED]>
Flex & Flash Consultant based in Cologne/Germany



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Ralf Bokelberg <[EMAIL PROTECTED]>
Flex & Flash Consultant based in Cologne/Germany __._,_.___

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