swift5 - 用户反馈（发送邮件）

// XXXViewController
var controller: MFMailComposeViewController?

func feedback() {
    if MFMailComposeViewController.canSendMail(){
        controller = MFMailComposeViewController()
        //设置代理
        controller?.mailComposeDelegate = self
        //设置主题
        controller?.setSubject("Feedback")
        //设置收件人
        controller?.setToRecipients(["lancexianghui@gmail.com"])
        //设置抄送人
        controller?.setCcRecipients([])
        //设置密送人
        controller?.setBccRecipients([])
        //设置邮件正文内容（支持html）
        controller?.setMessageBody("Please type here your issue or question:", isHTML: false)
        present(controller!, animated: true, completion: nil)
    } else {
        // 用户未建立邮箱账号，只有建立了邮箱账号才可发送邮件
        MessageManager.share.showMessage(theme: .warning, title: "Can't send mail on your device",  body: "Please setup an email account on the device.")
    }
}

// 代理 - 关闭邮件页面
extension XXXViewController: MFMailComposeViewControllerDelegate {
    func mailComposeController(_ controller: MFMailComposeViewController, didFinishWith result: MFMailComposeResult, error: Error?) {
        controller.dismiss(animated: true, completion: nil)
    }
}