On the web, a form posts its inputs because each one has a name. Mobile does the same thing, using HelixForm as the scope and Hx.Id as the name.

HelixForm

HelixForm is the mobile analog of web Helix's lava-form. It needs no prefix, and it is a VerticalStackLayout, so it stacks its children vertically and takes Spacing, Padding, and the rest.

<HelixForm Hx.Post="^/sink/contact" Hx.Notification="formErrors" Spacing="8">

    <ContentView Hx.Id="formErrors" />

    <Rock:FieldContainer Hx.Target="this" Hx.Swap="outer">
        <Rock:TextBox Hx.Id="email"
                      Label="Email"
                      IsRequired="True"
                      Hx.Post="^/sink/contact/email"
                      Hx.Trigger="Unfocused changed" />
    </Rock:FieldContainer>

    <Rock:FieldContainer>
        <Rock:TextBox Hx.Id="firstName" Label="First Name" IsRequired="True" />
        <Rock:TextBox Hx.Id="lastName" Label="Last Name" IsRequired="True" />
    </Rock:FieldContainer>

    <Button StyleClass="btn,btn-primary" Text="Submit" />
    <Button StyleClass="btn,btn-link" Text="Cancel" Command="{Binding PopPage}" />
</HelixForm>

The form carries the verb

Hx.Post goes on the HelixForm, not on the submit button. Any Button inside the form with no verb of its own and no Command is a submit button. That is the default, so the Submit button above needs no Helix attributes at all.

To opt a button out, give it any one of these:

• its own Command, which is what makes the Cancel button above a cancel button
• its own Hx.* verb, so it fires its own request instead
• Hx.Disable

Tapping the form's background does not submit it. Forms are excluded from natural tap wiring. If you genuinely want a tappable form surface, say so explicitly with Hx.Trigger="tapped".

Form behavior details

• Only Button submits by default, not ImageButton. An ImageButton that should submit needs its own verb.
• Depth does not matter. A button nested several layouts deep still submits, including one that arrives later in a fragment swapped into the form.
• If a submit button is tapped and the form declares no verb, nothing is sent.
• A submission's initiator is the form, not the button. So the form's Hx.Target, Hx.Swap, Hx.Confirm, and Hx.Notification are what apply. Putting Hx.Target on the submit button does nothing useful.

Inline validation, and why this matters

Look again at the email field above. Hx.Target="this" Hx.Swap="outer" sits on the FieldContainer, not on the TextBox. The TextBox inherits both, and this resolves to the element that declared it, which is the container. So every time the person leaves that field, the response replaces that one field's container in place.

Which means your endpoint has to return the field, not just a message. outer destroys the container it replaces, so whatever comes back is the field from then on. Return the whole container:

<Rock:FieldContainer Hx.Target="this" Hx.Swap="outer">
    <Rock:TextBox Hx.Id="email"
                  Label="Email"
                  IsRequired="True"
                  Text="{{ Form['email'] | Escape }}"
                  Hx.Post="^/sink/contact/email"
                  Hx.Trigger="Unfocused changed" />
    {% if isTaken %}
    <Label Text="That email is already in use." StyleClass="footnote, text-danger-strong" />
    {% endif %}
</Rock:FieldContainer>

Every attribute reappears, and each one breaks something different if you leave it out:

That is the standing cost of outer: it is the only swap that removes the element carrying your attributes, so the response has to re-declare them. See Requests and Targeting.

This is a direct port of HTMX's canonical inline validation pattern, and it is the clearest reason to understand Inheritance.

Automatic value inclusion

What gets included

• Inside a HelixForm, a submission includes every named, value-carrying control in the form.
• Outside a form, only the initiating element's own value is included, and only if it is a named input. Helix does not sweep up arbitrary siblings, matching HTMX.

A control with no name is never included. That is the mobile stand-in for HTML's "no name, no submit."

Naming a control: prefer Hx.Id

Either Hx.Id or x:Name gives a control the name its value is submitted under, and Helix checks Hx.Id first, so it wins if a control carries both. Prefer Hx.Id: it is the name Helix actually looks for, and it says plainly that the name exists for Helix rather than for something else. x:Name works only because MAUI mirrors it onto a property Helix falls back to.

The one place you still need x:Name is {x:Reference ...}, which resolves XAML names and cannot see an Hx.Id. If you need to both reference a control in a binding and submit its value, give it both.

How it travels

What the app can read

That last row surprises people. A bare MAUI Picker, DatePicker, CheckBox, or Slider contributes nothing, because none of them is a text input or a Switch. Use the Rock: equivalents, which report their own values:

Hx.Include

Inherits: no, deliberately.

Use it for values automatic inclusion cannot reach: something computed, or a control outside the initiator's scope.

<!-- A control the form does not contain, so automatic inclusion cannot see it. -->
<Rock:TextBox x:Name="promoCode" Label="Promo code" />

<Button Text="Submit" Hx.Post="^/sink/contact">
    <Hx.Include>
        <Rock:Parameter Name="promoCode" Value="{Binding Text, Source={x:Reference promoCode}}" />
        <Rock:Parameter Name="source" Value="mobile-app" />
    </Hx.Include>
</Button>

• Hx.Include merges over automatic inclusion. A parameter whose Name matches an automatically collected value replaces it rather than sending both.
• Bindings are evaluated at request time, so a value that changed since the screen loaded is current.
• A Parameter with a blank Name is skipped.

Hx.Params

Inherits: yes. none is the only supported value; anything else is ignored.

<Rock:TextBox Hx.Id="scratch" Label="Notes (not submitted)" Hx.Params="none" />

<!-- On a container, excludes the whole subtree. -->
<VerticalStackLayout Hx.Params="none">
    <Rock:TextBox Hx.Id="localFilter" />
</VerticalStackLayout>

Validation

Helix reuses the validation the app already has: IsRequired, ValidationExpression, and ValidationExpressionMessage on Rock fields, plus the Validator control.

There is no opt-in flag. When a validator is in play, it gates the request.

Inside a form

A form submission validates the form's visible fields automatically, before sending.

• An author-placed Rock:Validator inside the form is used as the summary, so you control where it appears.
• If you do not place one, a summary is inserted as the form's first child.
• The monitored field set is rebuilt on every submission, so fields swapped in between attempts are picked up.
• Hidden fields do not block submission, and Hx.Disable subtrees are skipped.

Validation runs only for a form submission. Inline field triggers inside the form, and buttons with their own verbs, are not submissions and skip it.

Outside a form: Hx.Validator

Inherits: yes. This one takes an object reference rather than an id, so unlike Hx.Target it cannot reach across a fragment boundary.

<Rock:Validator x:Name="checks">
    <Rock:Validator.ControlsToValidate>
        <x:Reference>email</x:Reference>
    </Rock:Validator.ControlsToValidate>
</Rock:Validator>

<Button Text="Send" Hx.Post="^/sink/contact" Hx.Validator="{x:Reference checks}" />

Failure shows the validator's messages and aborts. No request is sent.