Rails spinoffs - Nov 2006 - Event.observe: problem dynamically loading handler functions

I''m writing a script to generate a control panel form an XML file and
I''m having trouble when attempting to attach events using
Event.observer.

An example node in my XML file looks like this:

<control ... >
<function action="click" do="doSomething" />
</control>

where "click" is the event and "doSomething" is the name of
a
javascript function I have defined elsewhere.

My javascript looks something like this (the control nodes have already
been appended to the DOM as <a href..>''s):

var controls = $A(XML.getElementsByTagName("control"));
controls.each(function(node) {
			var nFunctions = $A(node.getElementsByTagName("function"));
			nFunctions.each(function(fun){
Event.observe(node.getAttribute("id"),fun.getAttribute("action"),fun.getAttribute("do"))
			});
		});

I know the problem is with the last argument in Event.observe because
if I change the last argument to an anonymous function it works. It
also works if I change the last argument so that it is the name of the
function. These both work:

Anonymous function:
Event.observe(node.getAttribute("id"),fun.getAttribute("action"),function(e){alert(e);})

Name of function:
Event.observe(node.getAttribute("id"),fun.getAttribute("action"),doSomething)

This is the error I''m getting:
[Exception... "Could not convert JavaScript argument" nsresult:
"0x80570009
(NS_ERROR_XPC_BAD_CONVERT_JS)" location: "JS frame::
http://.../prototype.js :: anonymous :: line 1969" data: no]

Any help greatly appreciated. Thanks!

.
James


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err... so, it works using eval

eval("Event.observe(node.getAttribute(''id''),fun.getAttribute(''action''),"+fun.getAttribute("do")+")");

I''m going to run with this for now, but I like to avoid eval so if
anyone has a better idea get at me.

Thanks,
James


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What you''re doing in the first example is essentially just passing a
string
in as the 3rd param, where it''s expecting a function pointer. It works
in
your eval because the whole statement is constructed as a string and then
interpreted.

If you are working in a object oriented context... where "myObj" is
some
object which has a function named "doSomething", the following will
work, as
it will return a pointer to the myObj.doSomething function... if you are
working with a only globally scoped functions, try replacing "myObj"
with
"window" below...

Event.observe(node.getAttribute(''id''),
fun.getAttribute(''action''), myObj[
fun.getAttribute(''do'')] );



On 11/8/06, James <brennanmusic-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
>
> err... so, it works using eval
>
>
eval("Event.observe(node.getAttribute(''id''),fun.getAttribute
>
(''action''),"+fun.getAttribute("do")+")");
>
> I''m going to run with this for now, but I like to avoid eval so if
> anyone has a better idea get at me.
>
> Thanks,
> James
>
>
> >
>

-- 
Ryan Gahl
Application Development Consultant
Athena Group, Inc.
Inquire: 1-920-955-1457
Blog: http://www.someElement.com


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Thanks Ryan, that did the trick!

.
James


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