ViewHelper Documentation
flux:outlet.validate
    ViewHelper to validate Outlet arguments
Use <flux:outlet.validate> inside the <flux.outlet.argument> viewHelper.
You can add any number of validations to the arguments. After submission
validation errors will be available inside the validationResults variable.
Example
<f:section name="Configuration">
     <flux:outlet>
          <flux:outlet.argument name="name">
               <flux:outlet.validate type="NotEmpty" />
          </flux:outlet.argument>
     </flux:outlet>
</f:section>
<f:section name="Main">
    <f:form noCache="1">
        <f:form.textfield name="name" value="{name}" />
        <f:if condition="{validationResults.name}">
            <f:for each="{validationResults.name}" as="error">
                <span class="error">{error.code}: {error.message}</span>
            </f:for>
        </f:if>
    </f:form>
</f:section>
Arguments
type string
validator to apply
options anySimpleType
additional validator arguments