Question

我是新手代码，我不知道如何摆脱我的可选值。我在某处读到这可能是我的问题。任何帮助都会很棒！

我一直在关注本教程：https://www.youtube.com/watch?v=Qyy8pJd4IWU

@IBAction func dropPhoto(sender: AnyObject) {

    presentViewController(imagePicker, animated: true, completion: nil)
}

func imagePickerController(picker: UIImagePickerController, didFinishPickingImage image: UIImage, editingInfo: [NSObject : AnyObject]?) {

    self.dismissViewControllerAnimated(true, completion: nil)

    let thumbnail = image.resizedImageWithContentMode(UIViewContentMode.ScaleAspectFit, bounds: CGSizeMake(400, 400), interpolationQuality: CGInterpolationQuality.High)
    let imgData = UIImagePNGRepresentation(thumbnail)
    let base64EncodedImage = imgData?.base64EncodedStringWithOptions(NSDataBase64EncodingOptions())

    let uniqueReference = firebase?.childByAutoId()
    uniqueReference!.setValue(base64EncodedImage)

    let key = uniqueReference?.key
    _ = mapView.userLocation.location
    geofire!.setLocation(mapView.userLocation.location,forKey: key)

}

Answer 1

每当看到此错误时，请查找“！”s

这里有两行包含force-unwrap

geofire!.setLocation(mapView.userLocation.location,forKey: key)

和

 uniqueReference!.setValue(base64EncodedImage)

你应该能够通过简单地替换它来解决它！用一个？，例如

geofire?.setLocation(mapView.userLocation.location,forKey: key)

只有当geoFire是实数值时才会调用setLocation，否则如果你还要处理nil情况，那么快速的方法是：

if let geoFire = geoFire {
      geoFire.setLocation(mapView.userLocation.location, forKey: key)
}
else{
     *do something*
}

Answer 2

您还可以在功能开头添加assert或precondition检查firebase和geofire。这是第三种方法，它将检查这些值并停止在调试版本上执行，否则只需返回发布版本。这将使后面的方法调用firebase和geofire安全。

您仍然需要确定为什么您的某个引用意外为零并处理该情况。也许永远不会首先调用这个图像选择器函数，或者只是删除assertFailure语句并让函数静默返回而不做任何事情。你的选择。

func imagePickerController(picker: UIImagePickerController, didFinishPickingImage image: UIImage, editingInfo: [NSObject : AnyObject]?) {
    guard let firebase = firebase else {
       assertionFailure("Missing Firebase reference")
       return
    }
    guard let geofire = geofire else {
       assertionFailure("Missing Geofire reference")
       return
    }
    self.dismissViewControllerAnimated(true, completion: nil)

    let thumbnail = image.resizedImageWithContentMode(UIViewContentMode.ScaleAspectFit, bounds: CGSizeMake(400, 400), interpolationQuality: CGInterpolationQuality.High)
    let imgData = UIImagePNGRepresentation(thumbnail)
    let base64EncodedImage = imgData.base64EncodedStringWithOptions(NSDataBase64EncodingOptions())

    uniqueReference = firebase.childByAutoId()
    uniqueReference.setValue(base64EncodedImage)
    geofire.setLocation(mapView.userLocation.location,forKey: uniqueReference.key)
}

致命错误：在展开可选值（lldb）时意外发现nil

2 个答案: