XForms/Conditional Styling

Motivation

You have a list of items that you want to display inside of a repeat loop. You want some items to have different styling based on the content of items.

Method

We will use the XForms group element to conditionally display an item inside of the repeat statement.

Sample XML Fragement

Assume your form has the following data in an instance:

<my-nodes>
   <my-node>
      <element1>true</element1>
      <element2>Element2 Value</element2>
   </my-node>
   <my-node>
      <element1>false</element1>
      <element2>Element2 Value</element2>
   </my-node>
   <my-node>
      <element1>true</element1>
      <element2>Element2 Value</element2>
   </my-node>
</my-nodes>

Conditional Display of Items

The following text will only output element2 when element1 has a value of true.

<xf:repeat nodeset="//my-node">
   <xf:group ref=".[element1='true']">
      <xf:output ref="element2"/>
   </xf:group>
</xf:repeat>

The syntax .[a='b'] says that from the current node if the element a equals the value b then output the elements within the group.

Conditional Formatting of Items

This same strategy can be used to enclose output in different div or span elements.

<xf:repeat nodeset="my-node">
   <xf:group ref=".[element1='true']">
      <xf:output ref="element2" class="strong"/>
   </xf:group>
   <xf:group ref=".[element1='false']">
      <xf:output ref="element2"/>
   </xf:group>
</xf:repeat>

In the above example all nodes with element1='true' will have a class="strong" in the output and any element with element1='false' will not have the attribute in the output.

Sample XForms Appliction

Load XForms Application

Source Code

In this example we need to display a list of synonyms for a specific term. The Synonyms are all listed and a preferred term is displayed with a bold font.

<html
   xmlns="http://www.w3.org/1999/xhtml"
   xmlns:ev="http://www.w3.org/2001/xml-events"
   xmlns:xsd="http://www.w3.org/2001/XMLSchema"
   xmlns:xf="http://www.w3.org/2002/xforms">
   <head>
       <title>Conditional Display</title>
       <style type="text/css">
          @namespace xf url("http://www.w3.org/2002/xforms");
          body {font-family:Helvetica, sans-serif}
          .strong {font-weight:bold;}
          /* this puts everything under the repeat element into a single line */
          xf|repeat * {display:inline;}
       </style>
       <xf:model>
          <xf:instance xmlns="" id="current-synset">
            <data>
               <synset-id>3</synset-id>
               <synonym>
                   <preferred>false</preferred>
                   <syn-name>Boolean-Value</syn-name>
               </synonym>
                <synonym>
                   <preferred>false</preferred>
                   <syn-name>Conditional-Value</syn-name>
               </synonym>
               <synonym>
                   <preferred>false</preferred>
                   <syn-name>Flag</syn-name>
               </synonym>
                <synonym>
                   <preferred>true</preferred>
                   <syn-name>Indicator</syn-name>
               </synonym>
                <synonym>
                   <preferred>false</preferred>
                   <syn-name>Yes/No-Value</syn-name>
               </synonym>
            </data>
          </xf:instance>
       </xf:model>
    </head>
    <body>
       <h3>Synonym Set</h3>
       <span>(preferred term is bold)</span><br/>
       <xf:label>Synonyms: </xf:label>
          <xf:repeat nodeset="instance('current-synset')/synonym" id="repeat">
             <xf:group ref=".[preferred='true']">
                <xf:output ref="syn-name" class="strong"/>
             </xf:group>
              <xf:group ref=".[preferred='false']">
                <xf:output ref="syn-name"/>
             </xf:group>  
          </xf:repeat>
    </body>
</html>

Discussion

XForms 1.1 also includes the if attribute. Some XForms can conditionally use this for display of elements.

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