public function init()
{
parent::init();
$this->basePath = Yii::getAlias($this->basePath);
if (!is_dir($this->basePath)) {
throw new InvalidConfigException("The directory does not exist: {$this->basePath}");
} elseif (!is_writable($this->basePath)) {
throw new InvalidConfigException("The directory is not writable by the Web process: {$this->basePath}");
} else {
$this->basePath = realpath($this->basePath);
}
$this->baseUrl = rtrim(Yii::getAlias($this->baseUrl), '/');
}