002: Contact form

A contact form that submits data to a server-side action, validates the input, and displays the result, all without a full page reload.

What this demonstrates

A server action is a Go struct that Piko exposes as a callable endpoint. Every action struct must embed piko.ActionMetadata. HTML name attributes map to Go struct fields through json tags. The validate tags document the rules and are consumed by code generation and tooling; Piko does not enforce them automatically before Call. Perform validation inside Call and return piko.ValidationField (single field) or piko.NewValidationError (multiple fields) for field-level errors.

The template uses p-on:submit.prevent to intercept form submission and call an action instead. The built-in $form variable serialises form fields for the action, so the template never has to read form values manually. Actions return a struct and an error, just like Render.

Project structure

src/
  pages/
    contact.pk                   The page: form template + Go script + CSS
  actions/
    contact/
      submit.go                  The server action that processes the form

How it works

The form uses p-on:submit.prevent="action.contact.Submit($form)" to intercept submission. $form serialises all named fields automatically.

The action defines three types. SubmitAction embeds piko.ActionMetadata for request context. SubmitInput is the input struct with json tags for field mapping and validate tags for rules. SubmitResponse holds the data that Piko returns to the client as JSON.

The action name follows convention. action.contact.Submit comes from the package directory (contact/) and the struct name minus the Action suffix.

type SubmitInput struct {
    Name    string `json:"name"    validate:"required"`
    Email   string `json:"email"   validate:"required,email"`
    Message string `json:"message" validate:"required,min=10"`
}

How to run this example

In the root directory of the Piko repository:

cd examples/scenarios/002_contact_form/src/
go mod tidy
air

See also