tapestry-core/src/test/app1/SelectZoneDemo.tml

<t:border xmlns:t="http://tapestry.apache.org/schema/tapestry_5_3.xsd">

    <div class="well">
        <dl class="dl-horizontal">
            <dt>Car Maker:</dt>
            <dd>${carMaker}</dd>
            <dt>Car Model:</dt>
            <dd>${carModel}</dd>
        </dl>
    </div>

    <t:form class="well">
        <t:errors/>

        <t:select t:id="carMaker" validate="required" t:mixins="formgroup"
                  model="makeModel" zone="modelZone" encoder="makeEncoder"/>

        <t:zone t:id="modelZone">
            <t:if test="carMaker">
                <t:delegate to="modelBlock"/>
            </t:if>
        </t:zone>

        <t:block id="modelBlock">
            <t:select t:id="carModel" model="availableModels" validate="required" blankOption="always"
                      t:mixins="formgroup"/>
        </t:block>

        <div class="form-actions">
            <t:submit value="literal:Submit" class="btn btn-primary"/>
        </div>
    </t:form>

</t:border>