Hi,

I’m trying to create a tool where there are several select parameters whose choices are determine by the previous parameter(s). I have a toy example with three parameters: Category, Food, and Prep method. Depending on the chosen Category, only certain Foods are shown, which in turn determines which Prep methods are available.

I’m trying to use the <options> tag with the “from_file” attribute. I have one column per parameter and one row per valid combination.

My problem is that the front end can get into a state where a certain valid combinations will be unselectable. In the example below, I can never select “Fruit”, “Kiwi”, and “Raw”. When I change the 1st select, the values for the 2^nd select are loaded, but the values for the 3^rd select cannot be updated. This is particularly problematic if there is only one choice for the 2^nd select, because I cannot get it’s “onchange” handler to fire (so the 3^rd select is always empty).

In my case, it would be nice if the first value of the 2^nd select is chosen as a default, and the 3^rd select is populated accordingly.

Any help would be appreciated. Perhaps I’m not using these features as intended, but it seemed like a natural application.

Thanks,

Josh

My data file looks like:

Meat    Chicken Fried

Meat    Chicken Grilled

Meat    Beef    Grilled

Meat    Beef    Stir-fried

Veg     Carrot  Boiled

Veg     Fennel  Raw

Fruit   Kiwi    Raw

And my tool’s <inputs> section is:

  <inputs>

    <param name="paramA" type="select" label="Category">

      <options from_file="test_select_options.txt">

        <column name="value" index="0"/>

        <column name="name" index="0"/>

        <filter type="unique_value" name="unique" column="0"/>

      </options>

    </param>

    <param name="paramB" type="select" label="Food" >

      <options from_file="test_select_options.txt">

        <column name="value" index="1"/>

        <column name="name" index="1"/>

        <filter type="unique_value" name="unique" column="1"/>

        <filter type="param_value" ref="paramA" name="A" column="0"/>

      </options>

    </param>

    <param name="paramC" type="select" label="How prepared">

      <options from_file="test_select_options.txt">

        <column name="value" index="2"/>

        <column name="name" index="2"/>

        <filter type="param_value" ref="paramA" name="A" column="0"/>

        <filter type="param_value" ref="paramB" name="B" column="1"/>

      </options>

    </param>

  </inputs>