src/Leevel/Mail/Mail.php
protected function callbackAttachment(Swift_Attachment $attachment, Closure $callbacks = null): IMail
    {
        if ($callbacks) {
            $callbacks($attachment, $this);
        }

        $this->message->attach($attachment);

        return $this;
    }
protected function callbackAttachment(Swift_Attachment $attachment, Closure $callbacks = null): IMail
    {
        if ($callbacks) {
            $callbacks($attachment, $this);
        }

        $this->message->attach($attachment);

        return $this;
    }
邮件附件消息回调处理.

@param \Swift_Attachment $attachment
@param null|\Closure     $callbacks

@return $this