Dependency drop down list

rubyonrails-talk
1

Hello,

     I am trying load a drop down list based on selection from first drop down list. Based on first drop down list selection, I am able to fetch data for second drop down list but I am not able to refresh second dropdown list contents.

How Can I refresh second drop list on selection of first drop down list, I have values for drop down list in an array.

2

You’d need to do this in Javascript using what’s called a “chained select”. There’s a variety of plugins that do this, but here’s one: Chained selects

You typically have two options:

  1. Write out all of the available options for your second select when the page loads, then selectively hide/show some of them depending on the first select’s selection.
  2. Make an ajax call back to your application when the first select is changed which will return to you the available options to populate the second select. This may be the best option if you have a lot of options in your selects. If you need to support clients that do not have javascript enabled: I’ve also seen option #1 done with optgroups, so you’d write out your second select with the corresponding options for each option in the first select nested within optgroups. You’d then selectively hide/show the options depending on what’s selected from the first select. The advantage here is that when JS is not available, the user just needs to scroll through the second select to find the options that correspond to their selection from the first select. It’s not ideal, but it’s a reasonable fallback.

Jim

3

You'd need to do this in Javascript using what's called a "chained select". There's a variety of plugins that do this, but here's one: Chained selects

You typically have two options:   • Write out all of the available options for your second select when the page loads, then selectively hide/show some of them depending on the first select's selection.
  • Make an ajax call back to your application when the first select is changed which will return to you the available options to populate the second select. This may be the best option if you have a lot of options in your selects. If you need to support clients that do not have javascript enabled: I've also seen option #1 done with optgroups, so you'd write out your second select with the corresponding options for each option in the first select nested within optgroups. You'd then selectively hide/show the options depending on what's selected from the first select. The advantage here is that when JS is not available, the user just needs to scroll through the second select to find the options that correspond to their selection from the first select. It's not ideal, but it's a reasonable fallback.

And I just want to add (just answered a couple questions in a row about this on SO) that you should not rely on stuffing HTML into the <select> tag to alter its options. This will work in a couple of browsers:

  document.getElementById('my_picker').innerHTML = '<option value="whatever">Whatever</option>';

but it will fail silently and weirdly in several others. The best way to build up a picker from an Ajax response is to get a JSON (or other array) of value/text pairs and build up the option elements inside a loop:

  myJSON.each(function(elm){     my_picker.options[my_picker.options.length] = new Option( elm['text'], elm['value'] );   });

Hope this helps,

Walter