problem with accessing functions

[[RaZoR]]

hello,

main script creates IE window, put an array there and then calls a child
script. chils script makes an array element equal to some object and
returns control to main script. then main script doesn't see that object
and its functions. why?

here is the code I implemented:

//in main script
oWSH = new ActiveXObject(W Script.Shell);
oIEWindow.docum ent.Script.MyAr ray = new Array()
oWSH.Run("child .js", 2, true);

//in child.js script
var MyObj = function() {
var Value = 3.14159;
var getValue = function() { return Value; }
var setValue = function(arg) { Value = arg; }
this.gV = getValue;
this.sV = setValue;
}
oIEWindow.docum ent.Script.MyAr ray[0] = new MyObj();
oIEWindow.docum ent.Script.MyAr ray[0].sV(2.71); // <-- this works
oIEWindow.docum ent.Script.MyAr ray[0].gV(); // <-- this works

//returning back to main
oIEWindow.docum ent.Script.MyAr ray[0].gV() // <-- this doesn't work

is it possible to set an object in array and call its functions from a
child script and then call'em again from main script?

what did I assume wrong in this code?

please help,
regards,
mirek

ps. I also tried the following definition of MyObj with no success:

var MyObj = function() {
mo = new Object();
mo.Value = 3.14159;
mo.gV = function() { return mo.Value; }
mo.sV = function(arg) { mo.Value = arg; }
return mo;
}

[kaeli]

Re: problem with accessing functions

In article <4GH5b.118164$2 k4.1281406@news .chello.at>,
nonexistent@ant ispam.address enlightened us with...[color=blue]
> hello,
>
> main script creates IE window, put an array there and then calls a child
> script. chils script makes an array element equal to some object and
> returns control to main script. then main script doesn't see that object
> and its functions. why?
>[/color]

[guess]
It's probably out of scope.

[color=blue]
> here is the code I implemented:
>
> //in main script
> oWSH = new ActiveXObject(W Script.Shell);
> oIEWindow.docum ent.Script.MyAr ray = new Array()
> oWSH.Run("child .js", 2, true);
>
> //in child.js script
> var MyObj = function() {[/color]

This var MuObj is not global (?). It will go out of scope and become
nothing when the child finishes. You don't return the object to a var in
the parent, like

var myObj = oWSH.Run("child .js",2,true);

That's a guess - I've never really done OOP JS. I do this in java,
though.
[color=blue]
>
> is it possible to set an object in array and call its functions from a
> child script and then call'em again from main script?
>[/color]

Well, I had a problem in JSP where the object being placed in the array
was actually a reference, not a copy, and the reference became nothing
when the scope reverted to main. I can't say if that's a problem for you
or not, as I've never tried this in JS.

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[[RaZoR]]

Re: problem with accessing functions

hi,
[color=blue]
> [guess]
> It's probably out of scope.[/color]

well, it looks like.. but I don't really understand.. the second
definition returns the object. I mean that "MyArray[0]" contains MyObj
object with its all methods (as I understand it). I also somehow
understand that first definition (without var mo = new Object()) can
loose its properties and methods, because it doesn't return anything to
MyArray[0] (but I am beginner and I doubt myself)

on the other side when I do a small change in code, namely I set
MyArray[0] in main script:

//in main script
oWSH = new ActiveXObject(W Script.Shell);
oIEWindow.docum ent.Script.MyAr ray = new Array()
oIEWindow.docum ent.Script.MyAr ray[0] = new MyObj(); // <-- added line
oWSH.Run("child .js", 2, true);

and then call child.js, everything works fine. from child.js I can call
MyArray[0].somefunction() and results are visible in main.js after
returning back.

generally I don't understand what's visible, what's not, and why in this
example..

regards,
mirek

[kaeli]

Re: problem with accessing functions

In article <ASI5b.119600$2 k4.1307382@news .chello.at>,
nonexistent@ant ispam.address enlightened us with...[color=blue]
>
> well, it looks like.. but I don't really understand.. the second
> definition returns the object.[/color]

Not to main, it doesn't. It returns it to another function in child. The
reference goes away when child is done.
[color=blue]
> on the other side when I do a small change in code, namely I set
> MyArray[0] in main script:
>
> //in main script
> oWSH = new ActiveXObject(W Script.Shell);
> oIEWindow.docum ent.Script.MyAr ray = new Array()
> oIEWindow.docum ent.Script.MyAr ray[0] = new MyObj(); // <-- added line
> oWSH.Run("child .js", 2, true);
>
> and then call child.js, everything works fine. from child.js I can call
> MyArray[0].somefunction() and results are visible in main.js after
> returning back.
>[/color]

Then the problem is indeed scope. You made a variable local to main and
child merely changed it, so it stayed there.
Using the "new" keyword makes a new object, so that object would be
local to child or main depending on where you put it.

Here's a couple good explanations of scope.

http://sharkysoft.com/tutorials/jsa/content/031.html

http://www.javaworld.com/javaworld/jw-01-1997/jw-01-javascript.html

[color=blue]
> generally I don't understand what's visible, what's not, and why in this
> example..
>[/color]

Well, scope works pretty much the same (excluding blocks in C) in all
the languages I've used...

outside any function...
var v = something;
v is global and visible anywhere

in function f...
var v = something;
v is local to f and not visible anywhere else.

in function g...
var x = v;
will fail if v was declared in f, will succeed if declared outside a
function.

So, if you have a main file with functions and statements, variables
declared outside any function are global and variables declared in a
function are local to that function and go away when the function is
done.

I am only vaguely familiar with WSH, so I am not sure what Run does. I
will assume it parses / executes "child.js" - therefore, anything in
child.js stays there. MyObj would be local to child.js and go away when
execution finishes (return control to main).

The solution, as you discovered, is to declare the object in main, then
execute the child.
You could probably also return the object and assign it to the array in
main, but I'm not certain. I don't think it would work the way you are
using the Run command, as I don't think you can return something that
way. If you were just using functions, it would work.

-------------------------------------------------
~kaeli~
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-------------------------------------------------

[[RaZoR]]

Re: problem with accessing functions

hello,
[color=blue][color=green]
>>well, it looks like.. but I don't really understand.. the second
>>definition returns the object.[/color]
>
> Not to main, it doesn't. It returns it to another function in child. The
> reference goes away when child is done.[/color]

to what function..? :( I don't understand that.. because actually both
main and client operate on the third, separate object: IE window with
its array.

it looks like this:
main creates this IE window via new ActivexObject and puts array there.
main initialize the [0]-element of this array as an MyObj object. then
main calls client as a separate process. client sees this IE window --
it looks for it and finds. then client calls MyArray[0] methods (which
is MyObj now set by main), and returns control back. then again main
sees the client's changes in IE window.

alternatively it looks like this:
main creates this IE window via new ActivexObject and puts array there.
then main calls client as a separate process. client does
MyArray[0]=MyObj, calls its [0]-element methods etc. after returning
back to main changes in IE window are not visible.
[color=blue]
> Here's a couple good explanations of scope.
> http://sharkysoft.com/tutorials/jsa/content/031.html
> http://www.javaworld.com/javaworld/j...avascript.html[/color]

surely I will put an eye there. thanks. :)
[color=blue]
> Well, scope works pretty much the same (excluding blocks in C) in all
> the languages I've used...[/color]

yes, but this is about "global" and "local" scope for *separate
processes*, not for functions.. does it propagate similar way?
[color=blue]
> I am only vaguely familiar with WSH, so I am not sure what Run does. I
> will assume it parses / executes "child.js" - therefore, anything in
> child.js stays there. MyObj would be local to child.js and go away when
> execution finishes (return control to main).[/color]

no, no.. Run executes another script as a separate process. as I
understand (please correct me), it is *completely separate*, except
envoironment variables in "USER" space. any communication between these
processes is then via this IE window, visible for main and client.
[color=blue]
> The solution, as you discovered, is to declare the object in main, then
> execute the child.[/color]

yes, but that ruins my algorithm a little :)
[color=blue]
> You could probably also return the object and assign it to the array in
> main, but I'm not certain. I don't think it would work the way you are
> using the Run command, as I don't think you can return something that
> way. If you were just using functions, it would work.[/color]

yes, it works for functions. but it is about processes. I would like to
return an object created in one process to another process via third
window, visible to both of them.

thanks ~kaeli~, I will look at those urls. As I know inter processes
communication differ from function-2-function.. If you think that I'm
wrong, please tell me..

regards,
mirek

[kaeli]

Re: problem with accessing functions

In article <STJ5b.120690$2 k4.1331644@news .chello.at>,
nonexistent@ant ispam.address enlightened us with...[color=blue][color=green]
>>[/color]
> to what function..? :( I don't understand that.. because actually both
> main and client operate on the third, separate object: IE window with
> its array.
>[/color]

That depends on the setup. From what you say below, I misworded my reply
because I didn't understand the whole of what you were doing. I kinda
still don't. :)

If you program in C, I could explain by saying you aren't extern-ing
your vars...
[color=blue]
> it looks like this:
> main creates this IE window via new ActivexObject and puts array there.
> main initialize the [0]-element of this array as an MyObj object. then
> main calls client as a separate process.[/color]

Key words - separate process. That process has its own space for things
(memory), often called a "heap". The "new" keyword allocates the space
on the *current* heap - the child's.
[color=blue]
> client sees this IE window --
> it looks for it and finds. then client calls MyArray[0] methods (which
> is MyObj now set by main), and returns control back. then again main
> sees the client's changes in IE window.
>[/color]

Main sees it because it was allocated during main and is in main's
memory heap (scope).
[color=blue]
> alternatively it looks like this:
> main creates this IE window via new ActivexObject and puts array there.[/color]

Array is a pointer to a block of memory. Empty memory. Just a space to
put stuff.
(js people correct me if I'm wrong, 'cuz I do this stuff in java and c)
[color=blue]
> then main calls client as a separate process.[/color]

Process gets its own heap. Allocates new objects to that space.
But the problem is this:
oIEWindow.docum ent.Script.MyAr ray[0] = new MyObj();

When that runs from child, MyObj points to a spot in the *child's* heap
- which disappears when the child process exits!
The array then points to dead space.
[color=blue]
> client does
> MyArray[0]=MyObj, calls its [0]-element methods etc. after returning
> back to main changes in IE window are not visible.
>[/color]

MyObj was allocated to the heap in child. When child process dies, heap
goes bye-bye. Array now points to nothing.
[color=blue]
>
> yes, but this is about "global" and "local" scope for *separate
> processes*, not for functions.. does it propagate similar way?
>[/color]

Yes.
As long as main is active, its heap is viable.
[color=blue][color=green]
> > The solution, as you discovered, is to declare the object in main, then
> > execute the child.[/color]
>
> yes, but that ruins my algorithm a little :)
>[/color]

Solutions often do. :)
[color=blue]
>
> yes, it works for functions. but it is about processes. I would like to
> return an object created in one process to another process via third
> window, visible to both of them.[/color]

There has to be a way, but I don't know it...

I'm now over my head a bit - did you try
microsoft.publi c* newsgroups? They do a bit more WSH and processes stuff
with IE than most...

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~kaeli~
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-------------------------------------------------

[[RaZoR]]

Re: problem with accessing functions

hi,
[color=blue][color=green]
>>alternative ly it looks like this:
>>main creates this IE window via new ActivexObject and puts array there.[/color]
>
> Array is a pointer to a block of memory. Empty memory. Just a space to
> put stuff.
> (js people correct me if I'm wrong, 'cuz I do this stuff in java and c)
>[color=green]
>> then main calls client as a separate process.[/color]
>
> Process gets its own heap. Allocates new objects to that space.
> But the problem is this:
> oIEWindow.docum ent.Script.MyAr ray[0] = new MyObj();
>
> When that runs from child, MyObj points to a spot in the *child's* heap
> - which disappears when the child process exits!
> The array then points to dead space.
>[color=green]
>>client does
>>MyArray[0]=MyObj, calls its [0]-element methods etc. after returning
>>back to main changes in IE window are not visible.[/color]
>
> MyObj was allocated to the heap in child. When child process dies, heap
> goes bye-bye. Array now points to nothing.[/color]

well.. if it is as you say then it starts to convice me :) Let me
summarize it:

main creates IE Window, and says "let there be an array". this is just
pointing to some place in memory, the beginning of the first element,
but "length" and it's end are unknown yet. then main executes MyArray[0]
= new MyObj() and by doing so, it really reserves a chunk of memory and
fills it with MyObj() elements. then main calls client. client can see
the object, even created by another process because MyObj[0] points
where MyObj *really* exists. after returning back mains sees the changes.

the alternative (doesn't work):
[...]unknown yet. then main calls client.js. client reserves and fills a
chunk of memory with MyObj() but this is at its own memory space.
(please correct me: if for example, in this very moment yet another
process wanted to execute MyArray[0] (via IE window) it would so
succesfully, right? because this object now *really* exists in memory,
and it doesn't matter where, because IE window MyArray[0] points exactly
there. right?). after returning back mains does not see the changes,
because MyArray[0] still points to a chunk of mamory, but this chunk
does not contain the object already.

right? :)

regards,
mirek

[kaeli]

Re: problem with accessing functions

In article <QlL5b.122774$2 k4.1373302@news .chello.at>,
nonexistent@ant ispam.address enlightened us with...[color=blue]
>
> well.. if it is as you say then it starts to convice me :) Let me
> summarize it:
>
> main creates IE Window, and says "let there be an array". this is just
> pointing to some place in memory, the beginning of the first element,[/color]

No - even more abstract. It points to the place the first element would
be at if there were a first element - which there isn't.

This is C, so forgive me if JS is more forgiving with pointers and
arrays and objects...

var MyArray;

myArray is now simply declared and points to nothing and its value is
NULL/undefined.

var myArray = new Array();

myArray, to the computer, now points to some memory address, say 12345,
that is the start of a block of memory large enough to hold an Array
object. That memory address either has nothing or has garbage. What it
doesn't have is any meaningful value.
[color=blue]
> but "length" and it's end are unknown yet. then main executes MyArray[0]
> = new MyObj() and by doing so, it really reserves a chunk of memory and
> fills it with MyObj() elements.[/color]

When main says
myArray[0] = new myObj();
the computer goes to 12345 and blocks out a chunk of memory large enough
to fit a myObj object in and initializes it however the constructor for
myObj tells it to.
[color=blue]
> then main calls client. client can see
> the object,[/color]

Client can see the object - as the object beginning at 12345 and ending
at 12345+size(myOb j).
[color=blue]
> even created by another process because MyObj[0] points
> where MyObj *really* exists. after returning back mains sees the changes.[/color]

Yup.
Any changes made by child change the contents of memory block 12345+size
(myObj).
[color=blue]
>
> the alternative (doesn't work):[/color]

myArray points to nothing. It is null. It has no memory block assigned.
[color=blue]
> [...]unknown yet. then main calls client.js. client reserves and fills a
> chunk of memory with MyObj() but this is at its own memory space.[/color]

Yup. The block is now 98765+size(myOb j).
[color=blue]
> (please correct me: if for example, in this very moment yet another
> process wanted to execute MyArray[0] (via IE window) it would so
> succesfully, right? because this object now *really* exists in memory,
> and it doesn't matter where, because IE window MyArray[0] points exactly
> there. right?).[/color]

You know, I can't be really sure on that. I don't do multithreading
well. Actually, I never do multithreading.
[color=blue]
> after returning back mains does not see the changes,[/color]

Because main still has array[0] pointing to 98765 - which no longer has
anything in it, since the child released it!

Does that help?

-------------------------------------------------
~kaeli~
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-------------------------------------------------

[[RaZoR]]

Re: problem with accessing functions

> Does that help?

yes! thanks a lot :)

regards,
mirek