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Radio

Radio renders a mutually‑exclusive choice set. Users can select exactly one option.

Signature​

choice := ui.Radio(label string, opts ...radio.Option) *radio.Value

Return value​

type Value struct {
    Value string // selected option label
    Index int    // zero‑based index in the options slice
}

If the user has never chosen an option and no default is set, choice is nil.

Option helpers​

HelperDescriptionDefault
radio.WithOptions("A", "B", ...)Provide the list of choices. Required.–
radio.WithDefaultValue("B")Pre‑select an option on first render (match by label).none
radio.WithRequired(true)Inside a Form the submit button is blocked until a choice is made.false
radio.WithDisabled(true)Greys out the entire group.false
radio.WithFormatFunc(func(v string,i int)string)Transform the displayed label (e.g. capitalise) while keeping the underlying value intact.identity

Behaviour notes​

  • State type – backend stores a single int32 index.
  • WithDefaultValue must match one of the option strings; otherwise no default is applied.
  • Changing the order of WithOptions between deployments will alter existing state.
  • FormatFunc is applied every render; it cannot depend on external mutable state unless the page is rerun.

Examples​

Basic radio​

color := ui.Radio("Primary colour",
    radio.WithOptions("Red", "Green", "Blue"),
)
if color != nil {
    fmt.Println("selected:", color.Value)
}

Default & required​

ui.Radio("Plan",
    radio.WithOptions("Free", "Pro", "Enterprise"),
    radio.WithDefaultValue("Pro"),
    radio.WithRequired(true),
)

Custom label formatting​

format := func(v string, _ int) string { return strings.ToUpper(v) }
ui.Radio("Priority",
    radio.WithOptions("low", "medium", "high"),
    radio.WithFormatFunc(format),
)

Disabled group​

ui.Radio("Archived",
    radio.WithOptions("Yes", "No"),
    radio.WithDisabled(true),
)