Rails spinoffs - Dec 2007 - Population of a drop down list (select) based upon another drop down selection

Suppose you have two related drop downs (selects) that you want to
populate from a
database. Assume one is Category, and the other is Subcategory.
When a Category is selected, you want the contents of the
Subcategory drop down to be populated with only those Subcategories
that are related to the Category selection.

Another example might be a role based access framework
and the first drop down is the controllers available for a given
right.  Once the user selects a controller, you want the next drop
down populated with only the actions available for that controller.

Being a Rails Newbie, I wasn''t sure I could tackle this on my own, but
it would be very useful.
After reading about script.aculo.us, it sounded like that might be in
the right direction.

Any suggestions on how to do this?  Keep in mind, i''m really new at
this....

Thank you!

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This can be done in straight Javascript.

You need two arrays (or a nice JSON oobject), a MAIN and a SUB.
MAIN contains name, value pairs. SUB contains name, value pairs AND
the member index from MAIN.
Call a function of the onchange event on the select containing the
MAIN list.

In this function first clear the SUB select box
(document.forms[''form1''].SUB.length=0) and loop through the
SUB array.
Where the main index value = the selected value from the main
selection, add that item to the SUB select like so:

 
document.forms[''form1''].SUB.options[document.forms[''form1''].SUB.length]
= new Option(name,val);

There might be an easier way to do this in Rails, but this will work.

On Dec 31 2007, 11:23 am, Crispy
<cris_palten...-/E1597aS9LQAvxtiuMwx3w@public.gmane.org>
wrote:
> Suppose you have two related drop downs (selects) that you want to
> populate from a
> database. Assume one is Category, and the other is Subcategory.
> When a Category is selected, you want the contents of the
> Subcategory drop down to be populated with only those Subcategories
> that are related to the Category selection.
>
> Another example might be a role based access framework
> and the first drop down is the controllers available for a given
> right.  Once the user selects a controller, you want the next drop
> down populated with only the actions available for that controller.
>
> Being a Rails Newbie, I wasn''t sure I could tackle this on my own,
but
> it would be very useful.
> After reading about script.aculo.us, it sounded like that might be in
> the right direction.
>
> Any suggestions on how to do this?  Keep in mind, i''m really new
at
> this....
>
> Thank you!
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