silverstripe-userforms/code/model/editableformfields/EditableRadioField.php

<?php
/**
 * EditableRadioField
 *
 * Represents a set of selectable radio buttons
 *
 * @package userforms
 */

class EditableRadioField extends EditableMultipleOptionField {

	private static $singular_name = 'Radio Group';

	private static $plural_name = 'Radio Groups';

	/**
	 * @return FieldList
	 */
	public function getCMSFields() {
		$fields = parent::getCMSFields();

		$fields->removeByName('Default');

		return $fields;
	}

	public function getFormField() {
		$field = OptionsetField::create($this->Name, $this->EscapedTitle, $this->getOptionsMap());
		$field->setFieldHolderTemplate('UserFormsMultipleOptionField_holder');

		// Set default item
		$defaultOption = $this->getDefaultOptions()->first();
		if($defaultOption) {
			$field->setValue($defaultOption->EscapedTitle);
		}
		$this->doUpdateFormField($field);
		return $field;
	}

	public function getSelectorField(EditableCustomRule $rule, $forOnLoad = false) {
		// We only want to trigger on load once for the radio group - hence we focus on the first option only.
		$first = $forOnLoad ? ':first' : '';
		return "$(\"input[name='{$this->Name}']{$first}\")";
	}
}