Form value adapter

Contract

Form values are read from a submitted form or a mounted form element through a Go API. The adapter returns ordinary Go data and does not require string event names.

import (
	"errors"

	"github.com/busdk/bus-gx/pkg/gx"
	gxwasm "github.com/busdk/bus-gx/pkg/gx/wasm"
)

func Editor() gx.Node {
	return (
		<form onSubmit={save}>
			<input name="title"></input>
			<input name="tag"></input>
			<input name="tag"></input>
			<button type="submit">Save</button>
		</form>
	)
}

func save(event gx.SubmitEvent) {
	values, err := gxwasm.FormValues(event)
	if err != nil {
		if errors.Is(err, gxwasm.ErrUnavailable) {
			reportBrowserUnavailable(err)
			return
		}
		report(err)
		return
	}
	title := values.Get("title")
	tags := values["tag"]
	saveDraft(title, tags)
}

The adapter preserves repeated field names. It exposes string values first; multipart file content belongs to the file adapter.

FormValues and MountedFormValues return net/url.Values. Get(name) returns the first value for a field. Indexing the map by field name returns the full slice in DOM insertion order, including repeated controls with the same name.

Mounted form reads use a CSS selector and return the same net/url.Values shape:

values, err := gxwasm.MountedFormValues("#note-editor")
if err != nil {
	report(err)
	return
}
title := values.Get("title")

An empty selector returns an error. A selector that does not match an element, or matches an element that is not a form, returns an error naming the selector problem. Host builds return errors matching gxwasm.ErrUnavailable.

Requirements

  • FormValues accepts submit-event form context when the callback was invoked from a form submit.
  • Mounted-form lookup is a browser adapter concern, not a GX node property.
  • Repeated field names remain addressable in insertion order.
  • Host builds return errors matching gxwasm.ErrUnavailable.
  • Browser calls without an active submit event also match gxwasm.ErrUnavailable.
  • Invalid mounted selectors return ordinary errors that name the selector problem, such as an empty selector or a selector that does not match a form.

Boundary

The form value adapter does not validate product input, authorize submission, upload files, execute resources, or choose which data to send. Application and library code decide that from ordinary Go state and callbacks.

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Sources