form

README

tinywasm/form

Fast form generation from Go structs for TinyGo + WASM. Uses fmt.Fielder interface for zero-reflection data binding.

Quick Start

// User struct implements fmt.Fielder (usually generated by ormc)
f, err := form.New("parent-id", &User{Name: "John"})
html := f.RenderHTML()    // render to HTML string

Public API

form.New(parentID string, data fmt.Fielder) (*Form, error)

Creates a Form from a Fielder.

• Uses data.Schema() to build inputs.
• Matches each field to a registered Input by name/alias or Field.Input.
• Copies data.Values() into inputs.
• Form id = parentID + "." + data.FormName().

form.RegisterInput(inputs ...input.Input)

Registers custom input types globally.

(*Form) Methods

Method	Description
GetID() string	Returns form's HTML id
SetSSR(bool) *Form	Enables SSR mode
RenderHTML() string	Generates form HTML
Validate() error	Validates all inputs
SyncValues(fmt.Fielder) error	Copies input values back into the provided data
ValidateData(byte, fmt.Fielder) error	Validates data (crudp.DataValidator)
OnSubmit(func(fmt.Fielder) error) *Form	Sets WASM submit callback
OnMount()	WASM only — sets up event delegation
Input(fieldName string) input.Input	Returns input for a field name

Migration Guide

If you were using form.New(parentID, &MyStruct{}), you must now ensure MyStruct implements fmt.Fielder. This is typically handled by tinywasm/orm's ormc tool.

API changes:

• SyncValues() → SyncValues(data)
• OnSubmit(func(any) error) → OnSubmit(func(fmt.Fielder) error)
• ValidateData(action, ...any) → ValidateData(action, fmt.Fielder)

Struct Tags

Tags are now parsed at generation time by ormc.

Tag	Format	Description
form	"email"	Force input type
form	"-"	Exclude from form
options	"k:v"	Select options
validate	"false"	Skip validation

Documentation Index

• SKILL.md — LLM compact reference (start here)
• API Reference
• Design & Architecture
• Struct Tags

Documentation

Index

• func GetTagOptions(fieldTag string) ([]fmt.KeyValue, bool)
• func ParseOptionsTag(tag string) []fmt.KeyValue
• func RegisterInput(inputs ...input.Input)
• func SetGlobalClass(classes ...string)
• type Form
  • func New(parentID string, data fmt.Fielder) (*Form, error)
  • func (f *Form) GetID() string
  • func (f *Form) Input(fieldName string) input.Input
  • func (f *Form) OnSubmit(fn func(fmt.Fielder) error) *Form
  • func (f *Form) ParentID() string
  • func (f *Form) RenderHTML() string
  • func (f *Form) SetID(id string)
  • func (f *Form) SetOptions(fieldName string, opts ...fmt.KeyValue) *Form
  • func (f *Form) SetSSR(enabled bool) *Form
  • func (f *Form) SetValues(fieldName string, values ...string) *Form
  • func (f *Form) SyncValues(data fmt.Fielder) error
  • func (f *Form) Validate() error
  • func (f *Form) ValidateData(action byte, data fmt.Fielder) error
• type Namer

Functions

func GetTagOptions

func GetTagOptions(fieldTag string) ([]fmt.KeyValue, bool)

GetTagOptions extracts options from a struct field tag using fmt.TagPairs.

func ParseOptionsTag

func ParseOptionsTag(tag string) []fmt.KeyValue

ParseOptionsTag parses "key1:text1,key2:text2" format into []fmt.KeyValue.

func RegisterInput

func RegisterInput(inputs ...input.Input)

RegisterInput registers input types for field mapping.

func SetGlobalClass

func SetGlobalClass(classes ...string)

Types

type Form

type Form struct {
	Inputs []input.Input
	// contains filtered or unexported fields
}

Form represents a form instance.

func New

func New(parentID string, data fmt.Fielder) (*Form, error)

New creates a new Form from a Fielder. parentID: ID of the parent DOM element where the form will be mounted. Returns an error if any exported field has no matching registered input.

func (*Form) GetID

func (f *Form) GetID() string

GetID returns the html id that group the form

func (*Form) Input

func (f *Form) Input(fieldName string) input.Input

Input returns the input with the given field name, or nil if not found.

func (*Form) OnSubmit

func (f *Form) OnSubmit(fn func(fmt.Fielder) error) *Form

OnSubmit sets the callback for form submission in WASM mode.

func (*Form) ParentID

func (f *Form) ParentID() string

ParentID returns the ID of the parent element.

func (*Form) RenderHTML

func (f *Form) RenderHTML() string

RenderHTML renders the form based on its SSR mode.

func (*Form) SetID

func (f *Form) SetID(id string)

SetID sets the html id that group the form

func (*Form) SetOptions

func (f *Form) SetOptions(fieldName string, opts ...fmt.KeyValue) *Form

SetOptions sets options for the input matching the given field name.

func (*Form) SetSSR

func (f *Form) SetSSR(enabled bool) *Form

SetSSR enables or disables SSR mode for this form.

func (*Form) SetValues

func (f *Form) SetValues(fieldName string, values ...string) *Form

SetValues sets values for the input matching the given field name.

func (*Form) SyncValues

func (f *Form) SyncValues(data fmt.Fielder) error

SyncValues copies all input values back into the bound struct via the Fielder's Pointers() method.

func (*Form) Validate

func (f *Form) Validate() error

Validate validates all inputs and returns the first error found.

func (*Form) ValidateData

func (f *Form) ValidateData(action byte, data fmt.Fielder) error

ValidateData validates a Fielder instance using this form's input rules. Satisfies the updated crudp.DataValidator interface (with fmt.Fielder).

type Namer

type Namer interface {
	FormName() string
}

Namer is optionally implemented by Fielder types to provide a custom name. If not implemented, the form derives the name from the first Schema field's context.