XForms/Conditional Styling

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Motivation[edit]

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[edit]

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

Sample XML Fragement[edit]

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[edit]

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[edit]

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[edit]

Load XForms Application

Source Code[edit]

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[edit]

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


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