How do I get the selected value from a collection_select in

I have the classic issue where I have two select boxes, the second’s
contents dependent on the first. I found some same code that works
fairly well using an Ajax.Updater. However, I need to pass in the
selected value of the original select list to the ajax call. I am
trying to use this[this.selectedIndex].value but keep getting a
“undefined local variable or method `this’ for #<#Class:0x3143860:

Any ideas? Here’s a my snippet of code from my view.

                        :id, :name,
                        {:prompt => "Select"},
                        html_options =
                               :onChange => "new

department_changed/’" + this[this.selectedIndex].value + “,



Hello Scott,

2007/2/21, Scott [email protected]:

Any ideas? Here’s a my snippet of code from my view.

You’re falling into the classic hole of Ruby vs JavaScript code.

department_changed/'" + this[this.selectedIndex].value + “,

Your onChange parameter must be a string that will be evaluated
client-side. The way your wrote it, you are calling this on the Rails
View object, which is the error you are getting.

You must either: escape your quotes, or use the %Q() operator to
enable you to use quotes inside a string, without escaping:

:onChange => %Q(
new Ajax.Updater(‘categories_span’, ‘/mgs/department_changed/’ +
this[this.selectedIndex].value, {asynchronous:true, evalScripts:true)

Hope that helps !

François Beausoleil

Hi François,

Thanks for getting back to me so quickly.

That sort of worked. When I wrap in the %Q, I get the following in the
source of the rendered page:

  <select id="product_departments" name="product[departments]"

onChange=“new Ajax.Updater(‘categories_span’,
department_changed/’ + this[this.selectedIndex].value + ,

Unfortunately, the controller is called when the item’s selection is

If I subsitute the this[this.selectedIndex].value with 4 for example,
just to see if it works, it does in fact update the second select box.

Any other ideas?

Thanks again,


On Feb 21, 9:11 pm, “François Beausoleil”