eZ Platform - update FieldDefinition Default Value

ezUpdateFieldDefDefaultValue.php

<?php

use eZ\Publish\Core\Base\Exceptions\ContentTypeFieldDefinitionValidationException;
use eZ\Publish\Core\FieldType\Country\Value as CountryValue;

$countryContentType = $contentTypeService->loadContentTypeByIdentifier('country_t');
$countryFieldDefinition = $countryContentType->getFieldDefinition('country');
$countryFieldType = $fieldTypeService->getFieldType(
    $countryFieldDefinition->fieldTypeIdentifier
);

$repository->beginTransaction();
try {
    $countryTypeDraft = $contentTypeService->createContentTypeDraft($countryContentType);
    $fieldDefinitionUpdateStruct = $contentTypeService->newFieldDefinitionUpdateStruct();
    $fieldDefinitionUpdateStruct->fieldSettings['isMultiple'] = false;
    $fieldDefinitionUpdateStruct->defaultValue = new CountryValue(
        [
            'PL' => [
                'Name' => 'Poland',
                'Alpha2' => 'PL',
                'Alpha3' => 'POL',
                'IDC' => 48,
            ],
            'NO' => [
                'Name' => 'Norway',
                'Alpha2' => 'NO',
                'Alpha3' => 'NOR',
                'IDC' => 47,
            ],
        ]
    );


    $contentTypeService->updateFieldDefinition(
        $countryTypeDraft,
        $countryFieldDefinition,
        $fieldDefinitionUpdateStruct
    );

    // Validate Default value 
    $countryTypeDraft = $contentTypeService->loadContentTypeDraft(
        $countryTypeDraft->id
    );
    $countryFieldDefinition = $countryTypeDraft->getFieldDefinition('country');
    $errors = $countryFieldType->validateValue(
        $countryFieldDefinition,
        $countryFieldDefinition->defaultValue
    );
    if (!empty($errors)) {
        throw new ContentTypeFieldDefinitionValidationException($errors);
    }

    $contentTypeService->publishContentTypeDraft($countryTypeDraft);

    $repository->commit();
} catch (\Exception $ex) {
    $repository->rollback();
    throw $ex;
}