Dynamic List Boxes

[MalCarne]

I've spent the better part of today googling dynamic select boxes and read a lot of ways to create them. However, none of the articles I've read address the lists being data driven.
So, here's what I've done and am trying to do. I start with a recordset and convert it into an array using .getrows
The array has 4 elements; ID, drug name, a delimited string of possible dosages, and a delimited string of possible quantities. The parent select is created like this:

<select name = drug onchange=fnDosage(this.options[options.selectedIndex].value,<%=arrDrug%>);>
       <option value=choose selected>..Choose..</option>
           <%  
             for i = 0 to ubound(arrDrug,2)
              drug_id = arrDrug(0,i)
              drug=arrDrug(1,i)
              if hist1 = drug_id then
                 selected = "Selected"
              end if
              response.Write("<option value="& i & selected & ">" & drug &"</option>")
               next  
              %>

What I'm trying to do is create 2 child selects; one for dosage, the other for quantity using the avalible values in the delimited strings in the array.
I have no idea if this is the right way to do this, but I want to keep form submission and database hits to a minimum.
Any suggestions?

 

[Sheco]

Your options, from easiest to hardest:

1. Use a page transion so that the user selects from first option list and submits form. The next page will then present a second list based on the option selected on the first page.

2. Use ASP to write all possibilites into client-side variables and then use client-side logic to populate the second list.

3. Use the client-side xmlhttp object to request data from an ASP that returns the second list of options in xml format... This is basically a remote procedure call. This technique is also known as AJAX.

 

[Tarwn]

I would suggest number 2. Output the javascrpt code for a dosage/quantity array thats indexes match the indexes of the select dropdown. Put an onChange in the select dropdown that calls a populate function with it's selected index. In the populate function, clear the child dropdowns, then loop through the portions of the javascript array for that index, creating a new option for each value and adding it to your second/third dropdown.

Here's how to build an array:

Response.Write "<script language=""javascript"">" & vbCrLf
Response.Write "var arrValues = new Array("
Dim rowCtr, lastVal
For rowCtr = 0 to UBound(myArr,2)
   'output a comma if we are on any record after the first one
   If rowCtr > 0 Then Response.Write ","

   'start two element array to hold arrays of dosages and amounts
   Response.Write "new Array("

   'output array of dosages - turn it into comma-delimited string with quotes around each value
   Response.Write "new Array('" & Replace(myArray(rowCtr,2),"','") & "'),"

   'output array of amounts
   Response.Write "new Array('" & Replace(myArray(rowCtr,3),"','") & "')"
   
   'end two element array
   Response.Write ")"
Next

'end outer array
Response.Write ");" & vbCrLf
Response.Write "</script>"
<%

Now, the array is technically 3 layers deep. The first layer should line up with the index for your dropdown, since it was filled from the same array. You will have to subtract 1 from the selected index to make it line up perfect since you have an extra option at the beginning of your dropdown. The second index is to choose either dosage [0] or amounts [1]. The third index is the dosage or amount indexes.

So if you wanted to loop through the array in javascript for a given index, it would be something like:

var myIndex = 5;
'loop through dosages
for(var i = 0; i < arrValues[myIndex][0].length;i++){
   alert("Dosage #" + i + " = " + arrValues[myIndex][0][i]);
}

'loop through amounts
for(var i = 0; i < arrValues[myIndex][1].length;i++){
   alert("Amount #" + i + " = " + arrValues[myIndex][1][i]);
}

Note: I have seen several of the ASP-driven cascading dropdown tutorials on the net. Mine (in the FAQs) is not all that great since it uses a fairly complex javascript array (I've been thinking about switching it), however everything else you need to know should be in there. Basically the only piece missing is to build a function to populate the two dropdowns based on the array values in the above code section.

-T

 

[MalCarne]

I'll give that a try. Thanks for the help.

 

[Bullschmidt]

And perhaps this may hopefully give you some ideas. It's got a downloadable sample and does retain values after the post back (although it is admittedly somewhat complicated):

Classic ASP Design Tips - Dependent Listboxes

http://www.bullschmidt.com/devtip-dependentlistboxes.asp

Best regards,
-Paul

http://www.Bullschmidt.com

- Freelance Web and Database Developer

http://www.Bullschmidt.com/DevTip.asp

- Classic ASP Design Tips