framework/mail/BaseMailer.php
protected function createView(array $config)
    {
        if (!array_key_exists('class', $config)) {
            $config['class'] = View::className();
        }

        return Yii::createObject($config);
    }
protected function createView(array $config)
    {
        if (!array_key_exists('class', $config)) {
            $config['class'] = View::className();
        }

        return Yii::createObject($config);
    }
Creates view instance from given configuration.
@param array $config view configuration.
@return View view instance.