ios - 局部变量声明 swift

Question

我试图允许用户在我的应用程序中发送电子邮件，但我收到:

Use of local variable 'configureMailComposeViewController' before its declaration

这是代码。

func item(_ item: Int, selectedAtContactIndex index: Int) {
    var mailComposeViewController = configuredMailComposeViewController()
    if MFMailComposeViewController.canSendMail() {
        self.presentViewController(mailComposeViewController, animated: true, completion: nil)
    } else {

    }
}

func configuredMailComposeViewController() -> MFMailComposeViewController{
    let mailComposerVC = MFMailComposeViewController()
    mailComposerVC.mailComposeDelegate = self

    mailComposerVC.setToRecipients([EmailAddressArray[index]])
    mailComposerVC.setSubject("I need your help")

    return mailComposerVC
}

Answer 1

func configuredMailComposeViewController() -> MFMailComposeViewController

这就是你的函数，它有一个返回类型MFMailComposeViewController，当你调用这个方法时你会得到它。它会返回一些结果

现在，您上述方法的结果 func configuredMailComposeViewController() -> MFMailComposeViewControllercall 需要保存在一个变量中，您不能让它在空中飞翔。为了保存或者获取执行此操作所需的任何方法 -:

var mailComposeViewController = configuredMailComposeViewController()

所以这清楚地表明您需要在返回函数之后而不是之前调用此 mailComposeViewController = configuredMailComposeViewController()。

正是这样——

    func configuredMailComposeViewController() -> MFMailComposeViewController{
        let mailComposerVC = MFMailComposeViewController()
        mailComposerVC.mailComposeDelegate = self

        mailComposerVC.setToRecipients([EmailAddressArray[index]])
        mailComposerVC.setSubject("I need your help")

        return mailComposerVC
    }





        func item(_ item: Int, selectedAtContactIndex index: Int) {

        if MFMailComposeViewController.canSendMail() {
var mailComposeViewController = configuredMailComposeViewController()
            self.presentViewController(mailComposeViewController, animated: true, completion: nil)
        } else {

        }
    }