XForms bind does not update when referenced instance data is updated - orbeon

Question

My problems is this:
I have 2 instances in my model:
<xf:instance id="Include-model">
<data>
<value type="xs:string">true</value>
</data>
</xf:instance>
this is wired up to a checkbox,
and
<xf:instance id="items-model">
<items>
<item>1</item>
<item>2</item>
<item>3</item>
</xf:instance>
and I have a bind declared as:
<xforms:bind id="items-bind" nodeset="items[instance('Include-model')/value = 'true']">
the checkbox correctly updates the Include-model, but the bind does not update to reflect this. Basically, if the checkbox is checked I need to display the items, otherwise hide them. The initial state is correct, but changes are not reflected in the bind when I check/uncheck the checkbox.
Eternal gratitude to all who can help.

Answer 1

You might try
<xforms:bind id="items-bind" nodeset="instance('items-model')" relevant="instance('Include-model')/value = 'true'" />

Answer 2

First up, I could see there are multiple issues in the code snippets you give here.
closing tag is missing here. It should look like
<xforms:instance id="items-model">
<items>
<item>1</item>
<item>2</item>
<item>3</item>
</items>
</xforms:instance>
The nodeset in the bind mentioned is for items. It should be for item. Since there is no information given whether it a code pulled from form-builder or "hand-written" code, i cannot say it is correct or not. For a "hand-written" codes the bind defnition in your case will look like this
<xforms:bind id="items-bind" nodeset="instance('items-model')/item[instance('Include-model')/value = 'true']" />
Below is the complete Xforms code you can run for this case. Try running with value as 'true' and again value as 'false' to understand how bind is working.
<xhtml:html xmlns:xhtml="http://www.w3.org/1999/xhtml"
xmlns:xxforms="http://orbeon.org/oxf/xml/xforms"
xmlns:xforms="http://www.w3.org/2002/xforms">
<xhtml:head>
<xhtml:title>Xforms</xhtml:title>
<xforms:model>
<xforms:instance id="Include-model">
<data>
<value type="xs:string">true</value>
</data>
</xforms:instance>
<xforms:instance id="items-model">
<items>
<item>1</item>
<item>2</item>
<item>3</item>
</items>
</xforms:instance>
<xforms:bind id="items-bind" nodeset="instance('items-model')/item[instance('Include-model')/value = 'true']" />
</xforms:model>
</xhtml:head>
<xhtml:body>
<table>
<tr>
<td>Bind items are
<xforms:output value="
string-join(xxforms:bind('items-bind'), ' -- ')
" />
</td>
</tr>
</table>
</xhtml:body>
</xhtml:html>