Orbeon: How to display dynamic dropdown values from file system resource - forms

Question

I am new to Orbeon and trying to implement a dynamic dropdown where the values are populated from a lookup xml on file system.
So here's the requirement:
The first dropdown (Animal) will have 2 values: Cat and Dog. Based on the selection, the second dropdown (Breeds) will display the list of breeds.
The 2 xml files containing the breeds are registered as resources and look like this:
CAT: \forms\quote\lookup\catbreeds.xml
<?xml version="1.0" encoding="UTF-8"?>
<breeds>
<item>
<value>C1</value>
<label>Domestic Long Hair</label>
</item>
<item>
<value>C2</value>
<label>Domestic Medium Hair</label>
</item>
<item>
<value>C3</value>
<label>Domestic Short Hair</label>
</item>
<item>
<value>C4</value>
<label>Mixed Breed</label>
</item>
<item>
<value>C5</value>
<label>Tabby</label>
</item>
<item>
<value>C6</value>
<label>Abyssinian</label>
</item>
<item>
<value>C7</value>
<label>American Bobtail</label>
</item>
</breeds>
DOG: \forms\quote\lookup\dogbreeds.xml
<?xml version="1.0" encoding="UTF-8"?>
<breeds>
<item>
<value>D1</value>
<label>Cavapoo</label>
</item>
<item>
<value>D2</value>
<label>Cockapoo</label>
</item>
<item>
<value>D3</value>
<label>Crossbreed</label>
</item>
<item>
<value>D4</value>
<label>Goldendoodle</label>
</item>
<item>
<value>D5</value>
<label>Labradoodle</label>
</item>
<item>
<value>D6</value>
<label>Maltipoo</label>
</item>
<item>
<value>D7</value>
<label>Mi Ki</label>
</item>
</breeds>
The form.xml looks like this:
Model:
<xf:instance id="fr-form-instance" xxf:exclude-result-prefixes="#all">
<form>
<section-1>
<animal/>
<breed/>
</section-1>
</form>
</xf:instance>
<xf:instance id="pets"
xmlns="">
<root>
<item name="Cat" value="cat"/>
<item name="Dog" value="dog"/>
</root>
</xf:instance>
Body:
<xh:body>
<fr:view>
<fr:body
xmlns:oxf="http://www.orbeon.com/oxf/processors"
xmlns:p="http://www.orbeon.com/oxf/pipeline"
xmlns:xbl="http://www.w3.org/ns/xbl">
<fr:section id="section-1-control" class="no-header-section" bind="section-1-bind">
<fr:grid>
<xh:tr>
<xh:td>
<fr:dropdown-select1 id="animal-control" ref="animal" bind="breed-bind">
<xf:label ref="$form-resources/animal/label"/>
<xf:itemset ref="instance('pets')/item">
<xf:label ref="#name"/>
<xf:value ref="#value"/>
</xf:itemset>
</fr:dropdown-select1>
</xh:td>
</xh:tr>
<xh:tr>
<xh:td>
<fr:dropdown-select1 id="breed-control" bind="breed-bind">
<xf:label ref="$form-resources/breed/label"/>
<xf:itemset
ref="doc('oxf:/forms/quote/lookup/catbreeds.xml')/breeds/item">
<xf:label ref="label"/>
<xf:value ref="value"/>
</xf:itemset>
</fr:dropdown-select1>
</xh:td>
</xh:tr>
</fr:grid>
</fr:section>
</fr:body>
</fr:view>
</xh:body>
Now, the "ref" attribute in ref="doc('oxf:/forms/quote/lookup/catbreeds.xml')/breeds/item"> is where the problem is. I am able to load the individual lists (in this case it loads Cat breeds) but I am not able to find a way to make it conditional.
I found that I cannot use XPath for ref (like this:oxf:/forms/quote/lookup/{animal}breeds.xml) to make the value dynamic.
I have been trying a lot of things but nothing is working out. It will be a great help if someone can give me a direction.
I'm on Orbeon 4.8

Answer 1

Since the value of ref is XPath, you can build the URL you pass to doc() dynamically, by doing something along these lines:
doc(concat(
'oxf:/forms/quote/lookup/',
instance('fr-form-instance')/section-1/animal,
'breeds.xml'
))/breeds/item