CheckableVisibilityField::getCheckbox PHP Method

    public function getCheckbox()
    {
        return $this->checkbox;
    }

 /**
  * Hook into the updateProfileFields function to swap out the email field with our own custom Field.
  * @param  FieldList $fields
  */
 public function updateProfileFields(FieldList $fields)
 {
     // Get a reference to the MemberProfilePage
     $owner = $this->getOwner();
     // Get the Email Profile Field
     $profileField = $owner->Fields()->filter(array('MemberField' => 'Email'))->first();
     if (!$profileField || !$profileField->ID || $profileField->AllowedDomains && $profileField->DisallowedDomains) {
         // If we can't find the Email Profile Field or if there's no domain condition on the field,
         // there's no point carrying on
         return;
     }
     // Get the actual Email Form Field
     $oldField = $fields->fieldByName('Email');
     if (!$oldField) {
         // IF we can't find the form field.
         return;
     }
     // The form field might come as a CheckableVisibilityField or a TextField.
     // We need to handle both case differently
     if (is_a($oldField, 'CheckableVisibilityField')) {
         // Create our new DomainSpecificEmailField
         $field = $this->initNewField($oldField->getChild(), $profileField);
         // We need to replicate a bit of logic from MembrProfilePage::getProfileFields()
         $field = new CheckableVisibilityField($field);
         if ($profileField->PublicVisibility == 'Display') {
             $field->makeAlwaysVisible();
         } else {
             $field->getCheckbox()->setValue($profileField->PublicVisibilityDefault);
         }
     } else {
         // Just convert the Email Form Field to our DomainSpecificEmailField
         $field = $this->initNewField($oldField, $profileField);
     }
     // Swap our the old field with the new one.
     $fields->replaceField('Email', $field);
 }