silverstripe-userforms/code/model/formfields/EditableCheckbox.php

<?php
/**
 * EditableCheckbox
 *
 * A user modifiable checkbox on a UserDefinedForm
 * 
 * @package userforms
 */

class EditableCheckbox extends EditableFormField {
	
	private static $singular_name = 'Checkbox Field';
	
	private static $plural_name = 'Checkboxes';

	private static $db = array(
		'CheckedDefault' => 'Boolean' // from CustomSettings
	);

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

		$fields->replaceField('Default', CheckboxField::create(
			"CheckedDefault",
			_t('EditableFormField.CHECKEDBYDEFAULT', 'Checked by Default?')
		));

		return $fields;
	}

	public function getFormField() {
		$field = CheckboxField::create($this->Name, $this->Title, $this->CheckedDefault);
		
		if ($this->Required) {
			// Required validation can conflict so add the Required validation messages
			// as input attributes
			$errorMessage = $this->getErrorMessage()->HTML();
			$field->setAttribute('data-rule-required', 'true');
			$field->setAttribute('data-msg-required', $errorMessage);
		}
		
		return $field;
	}
	
	public function getValueFromData($data) {
		$value = (isset($data[$this->Name])) ? $data[$this->Name] : false;
		
		return ($value) ? _t('EditableFormField.YES', 'Yes') : _t('EditableFormField.NO', 'No');
	}

	public function migrateSettings($data) {
		// Migrate 'Default' setting to 'CheckedDefault'
		if(isset($data['Default'])) {
			$this->CheckedDefault = (bool)$data['Default'];
			unset($data['Default']);
		}
		
		parent::migrateSettings($data);
	}
}