swift - fatal error : unexpectedly found nil while unwrapping an Optional value when saving NSData to Realm

Question

我想用 Realm 保存来自 imagePicker 的图像。当我选择一张图片时它有效，但当我不选择一张图片时它不起作用。我尝试在未选择图像时保存标准图像。但我收到错误: fatal error :在展开可选值时意外发现 nil地点:

class Location: Object{
dynamic var name = ""
dynamic var locationDescription = ""
dynamic var latitude = 0.0
dynamic var longitude = 0.0
dynamic var created = NSDate ()
dynamic var category: Category!
dynamic var imageData: NSData!
}

添加新的入口 Controller :

 //Image Picker
@IBOutlet var imageView: UIImageView!
let imagePicker = UIImagePickerController()
var selectedImage = UIImage()


@IBAction func loadImage(_ sender: AnyObject) {
    imagePicker.allowsEditing = true
    imagePicker.sourceType = .photoLibrary
    imagePicker.mediaTypes =     UIImagePickerController.availableMediaTypes(for: .photoLibrary)!
    present(imagePicker, animated: true, completion: nil)
    }
//MARK: - Delegates Image Picker
func imagePickerController(_ picker: UIImagePickerController,
                           didFinishPickingMediaWithInfo info: [String : Any])
{
    selectedImage = info[UIImagePickerControllerOriginalImage] as! UIImage

    imageView.image = selectedImage

    // Dismiss the picker.
    self.dismiss(animated: true, completion: nil)

}
func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
    dismiss(animated: true, completion: nil)
}

func addNewLocation() {
    let realm = try! Realm()
    //convert image to NSData
    let standardData: NSData = UIImagePNGRepresentation(self.imageView.image!)! as NSData
    let selctedImageData = NSData(data: UIImageJPEGRepresentation(selectedImage, 0.9)!)
    let emptyData = NSData()
   // let data = NSData(data: UIImageJPEGRepresentation(selectedImage, 0.9)!)
    var data = NSData()

    if selctedImageData == emptyData{
        data = standardData
    }
    else{
        data = selctedImageData
    }

    try! realm.write {
        let newLocation = Location()


        newLocation.name = self.nameTextField.text!
        newLocation.category = self.selectedCategory
        newLocation.locationDescription = self.descriptionTextField.text
        newLocation.latitude = self.selectedAnnotation.coordinate.latitude
        newLocation.longitude = self.selectedAnnotation.coordinate.longitude
        newLocation.imageData = data


        realm.add(newLocation)
        self.locations = newLocation
    }
}

编辑:我用查询生成的字符串替换了类别模型。

class Location: Object{
...
dynamic var category = ""
dynamic var imageData: NSData!

}

Answer 1

您的 Location 模型有两个隐式解包选项 (IUO) 属性:category 和 imageData。当您知道该值可能必须存储 nil 时，Swift 中的 IUO 非常有用，但您可以保证它永远不会在该状态下被访问，而编译器无法自动暗示。

在这种情况下，您在将其中一个属性的值设置为 nil 以外的值之前先访问该属性。

也许self.selectedCategory在分配给newLocation.category属性时是nil？鉴于您的示例中没有包含与此值相关的任何内容，所以很难说。

如果您不能保证这些 IUO 在访问时会被设置为非零，我建议您将它们定义为可选值，并专门处理它们的零情况。

class Location: Object {
  dynamic var name = ""
  dynamic var locationDescription = ""
  dynamic var latitude = 0.0
  dynamic var longitude = 0.0
  dynamic var created = NSDate()
  dynamic var category: Category?
  dynamic var imageData: NSData?
}