Re: FLASH: Eval or not to Eval

[Gregg Caines]

eval takes a string and returns the value of a variable

that has the same name as a string.


If you have a variable called var1 and its value is 123

then saying trace(var1) will give you 123 as output.


If instead you said trace("var1") you will get "var1" as

output.


If your variable name is in string form like the one above

you would have to say trace(eval("var1")) to get the

output 123.


In this context it seems useless, but it's great for faking

arrays (lists of variables) because you can do

eval("array"&x) where x is an integer value which can

change depending on which item in the list you want.

Just by using eval and changing the value of x (like in a

loop) you can automatically fake an array and have

access to an entire list of variables at runtime.  If x = 1

then eval("array"&x) will be referring a variable called

array1.  Incrementing the value of x is an easy way of

using variables named array2, array3, array4, etc,etc...


It is one of the more confusing concepts but it is really

useful.


---------------------------------------------------

Gregg Caines

n e o m e t r i x  systems inc.

http://www.neometrixsystems.com

gcainesneometrixsystems [dot] com

> Hi Flashers,

>

> I am hoping that somebody in a clear and concise manner can explain the

purpose and function of the Eval function in the action script editor. I

thought I understood the purpose of it and even attempted the flash example

in the manual which was working fine, however it is really a mystery to me

how it actually works, this feature seems especially important and now that

I want to start projects using speed and friction, for example, it is

essential I get it clear how to use it. Please I beg you I have been pacing

around trying to understand its use and application, and the general

descriptions from other sites are not helping, they are just making it more

confusing for me. I really need an idiots guide to its working and why to

use it.

>

> for example what is the difference between using Eval and just using the

variable in a loop????

>

> anyway the carpet is wearing thin look forward to your replys

>

> Stuart

>

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