Swift中的MFMailComposeViewController

Question

这是示例代码:

import UIKit
import MessageUI

class ViewController: UIViewController, MFMailComposeViewControllerDelegate {

    @IBAction func showEmail(sender : AnyObject) {
        var emailTitle = "Test Email"
        var messageBody = "This is a test email body"
        var toRecipents = ["a.nakhimov@gmail.com"]
        var mc: MFMailComposeViewController = MFMailComposeViewController()
        mc.mailComposeDelegate = self
        mc.setSubject(emailTitle)
        mc.setMessageBody(messageBody, isHTML: false)
        mc.setToRecipients(toRecipents)

        self.presentViewController(mc, animated: true, completion: nil)
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }

    func mailComposeController(controller:MFMailComposeViewController, didFinishWithResult result:MFMailComposeResult, error:NSError) {
        switch result {
        case MFMailComposeResultCancelled:
            NSLog("Mail cancelled")
        case MFMailComposeResultSaved:
            NSLog("Mail saved")
        case MFMailComposeResultSent:
            NSLog("Mail sent")
        case MFMailComposeResultFailed:
            NSLog("Mail sent failure: %@", [error.localizedDescription])
        default:
            break
        }
        self.dismissViewControllerAnimated(false, completion: nil)
    }
}

在函数mailComposeController中,我在每个case表达式上都得到一个错误:

找不到接受提供的参数的重载'〜='.

我究竟做错了什么？

Answer 1

我比较MFMailComposeResult了Xcode 5和Xcode 6上的文档.在Swift中,MFMailComposeResult是一个结构

struct MFMailComposeResult {
    init(_ value: CUnsignedInt) // available in iPhone 3.0
    var value: CUnsignedInt
}

用MFMailComposeResultCancelled类型的一个常数MFMailComposeResult:

var MFMailComposeResultCancelled: MFMailComposeResult { get }

虽然它是Objective-C中的枚举:

 enum MFMailComposeResult {
    MFMailComposeResultCancelled,
    MFMailComposeResultSaved,
    MFMailComposeResultSent,
    MFMailComposeResultFailed
};
typedef enum MFMailComposeResult MFMailComposeResult;   // available in iPhone 3.0

为了使您的代码有效,您必须比较它们的值CUnsignedInt.

所以你必须输入以下代码:

func mailComposeController(controller:MFMailComposeViewController, didFinishWithResult result:MFMailComposeResult, error:NSError) {
    switch result.value {
    case MFMailComposeResultCancelled.value:
        println("Mail cancelled")
    case MFMailComposeResultSaved.value:
        println("Mail saved")
    case MFMailComposeResultSent.value:
        println("Mail sent")
    case MFMailComposeResultFailed.value:
        println("Mail sent failure: \(error.localizedDescription)")
    default:
        break
    }
    self.dismissViewControllerAnimated(false, completion: nil)
}

Answer 2

在Swift 2.0中执行此操作:

func mailComposeController(controller: MFMailComposeViewController, didFinishWithResult result: MFMailComposeResult, error: NSError?) {
        switch result.rawValue {
        case MFMailComposeResultCancelled.rawValue:
            print("Mail cancelled")
        case MFMailComposeResultSaved.rawValue:
            print("Mail saved")
        case MFMailComposeResultSent.rawValue:
            print("Mail sent")
        case MFMailComposeResultFailed.rawValue:
            print("Mail sent failure: \(error!.localizedDescription)")
        default:
            break
        }
        controller.dismissViewControllerAnimated(true, completion: nil)
    }

Answer 3

在swift 3.0中 - >语法更改

func mailComposeController(controller: MFMailComposeViewController,
                           didFinishWithResult result: MFMailComposeResult, error: NSError?) {

    switch result.rawValue {
    case MFMailComposeResult.Cancelled.rawValue:
        print("Mail cancelled")
    case MFMailComposeResult.Saved.rawValue:
        print("Mail saved")
    case MFMailComposeResult.Sent.rawValue:
        print("Mail sent")
    case MFMailComposeResult.Failed.rawValue:
        print("Mail sent failure: %@", [error!.localizedDescription])
    default:
        break
    }
    // Dismiss the mail compose view controller.
    controller.dismissViewControllerAnimated(true, completion: nil)
}