iOS 发送电子邮件或短信时出错

Question

我尝试从 iOS 应用发送短信和电子邮件，但遇到了一些问题。

我从教程中获取了代码，例如短信代码:

func sendMessage() {
    let prefs = NSUserDefaults.standardUserDefaults()
    var message = MFMessageComposeViewController()

    // Contacts
    var phoneNumbers = [String]()
    var phoneNumberNb: Int = prefs.objectForKey("phonenumberssaved")!.count
    for(var i = 0; i < phoneNumberNb; i++) {
        phoneNumbers.append(prefs.objectForKey("phonenumberssaved")!.objectAtIndex(i) as! String)
    }

    println(phoneNumbers)

    message.recipients = phoneNumbers
    message.body = self.messageText
    message.messageComposeDelegate = self

    self.presentViewController(message, animated: false, completion: nil)
} 

我打印了我的数据(它们似乎没问题)，但是当我尝试发送它时，应用程序崩溃并显示

'fatal error: unexpectedly found nil while unwrapping an Optional value' and it show me a strange file with a line highlighted : '0x4b5164 <+64>: trap'...

Answer 1

使用条件展开。另外，您不需要处理每个数组元素:

func sendMessage() {
    let prefs = NSUserDefaults.standardUserDefaults()
    let message = MFMessageComposeViewController()

    // Contacts
    if let phoneNumbers = prefs.objectForKey("phonenumberssaved") as? [String] {
        println(phoneNumbers)

        message.recipients = phoneNumbers
        message.body = "some body"
        message.messageComposeDelegate = self

        self.presentViewController(message, animated: false, completion: nil)
    }
}