MFMailComposeViewController Delegate 没有在其他类中被调用 swift 4

Question

我有这个代码，它关于 didFinishWith 结果的问题没有被调用并且应用程序崩溃。这是我的代码

注意：在 Objective C 中，这段代码可以正常工作，因为我在我的类中创建了一个强引用，但我在 Swift 中遇到了问题，我不知道如何解决这个问题

import Foundation
import MessageUI

class EmailCreator: NSObject, MFMailComposeViewControllerDelegate {
    // in other class I send this var to show email
    var viewToShow = UIViewController ()

    func sendEmail() {

        let mailComposeViewController = createMailComposeViewController()
        if MFMailComposeViewController.canSendMail(){
            viewToShow.present(mailComposeViewController, animated: true, completion: nil)
        }else{
            print("Can't send email")
        }
    }

    func createMailComposeViewController() -> MFMailComposeViewController {
        let mailComposeViewController = MFMailComposeViewController()
        mailComposeViewController.mailComposeDelegate = self
        mailComposeViewController.setToRecipients(["example@test.test"])
        mailComposeViewController.setSubject("subject")
        mailComposeViewController.setMessageBody("test body", isHTML: false)
        return mailComposeViewController
    }
    //MARK: - MFMail compose method
    func mailComposeController(_ controller: MFMailComposeViewController, didFinishWith result: MFMailComposeResult, error: Error?) {
        controller.dismiss(animated: true, completion: nil)
    }
}

在其他班级我有这个代码来显示电子邮件：

@IBAction func sendEmail(_ sender: UIButton) {

        let email = EmailCreator()
        email.viewToShow = self
        email.sendEmail()
}

Answer 1

它崩溃是因为你有 EmailCreator，一个本地变量 MFMailComposeViewController 的代表，如你的 func createMailComposeViewController 所示。当MFMailComposeViewController 调用didFinishWith 方法时，EmailCreator 已经是deinited。 您可以通过将 EmailCreator 实例设为强属性来解决此问题。

YourViewController: UIViewController {
    let email = EmailCreator()

     @IBAction func sendEmail(_ sender: UIButton) {
        email.viewToShow = self
        email.sendEmail()
    }
}