XForms/Limiting Length

Motivation

You want to warn a user that an input control exceeds a specified length.

Method

We will use the XForms "action" element and conditionally display a message if the string-length is larger than 50 characters. The following action should be placed within the control.

<xf:action ev:event="xforms-value-changed" if="string-length(.) &gt; 50">
   <xf:message level="modal">maximum length is 50 characters</xf:message>
</xf:action>

Example with Textarea

<xf:textarea ref="short-message" incremental="true">
   <xf:label>Message:</xf:label>
      <xf:action ev:event="xforms-value-changed" if="string-length(.) &gt; 140">
         <xf:message level="modal">Maximum message length is 140 characters.</xf:message>
      </xf:action>
</xf:textarea>
<xf:output ref="short-message"/>