ios - 无法使用类型为 '[String : Any]' 的索引下标类型为 'UIImagePickerController.InfoKey' 的值

Question

我正在使用 Apple's Swift iOS Tutorial .这是抛出错误，

Cannot subscript a value of type '[String : Any]' with an index of type 'UIImagePickerController.InfoKey'

他们定义的函数如下。

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {

    // The info dictionary may contain multiple representations of the image. You want to use the original.
    guard let selectedImage = info[UIImagePickerControllerOriginalImage] as? UIImage else {
        fatalError("Expected a dictionary containing an image, but was provided the following: \(info)")
    }

    // Set photoImageView to display the selected image.
    photoImageView.image = selectedImage

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

我使用的是 Xcode 版本 10.0 beta 3，其中包括 Swift 4.2。

我想了解如何遍历文档以了解可能已更改或损坏的内容。

Answer 1

方法的签名在 Swift 4.2 中发生了变化

func imagePickerController(_ picker: UIImagePickerController, 
  didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any])

你必须写

guard let selectedImage = info[.originalImage] as? UIImage else {
    fatalError("Expected a dictionary containing an image, but was provided the following: \(info)")
}

您可以通过阅读 documentation 自行了解此类术语更改。或者通过注释掉整个方法，重新键入前几个字符并使用代码完成。