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

Question

I'm using Apple's Swift iOS Tutorial. Which is throwing an error,

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

The function they defined is below.

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) } 

I'm using Xcode Version 10.0 beta 3, which includes Swift 4.2.

I'd like to understand how to traverse the docs to understand what might have changed or broken.

Answer 1

The signature of the method has changed in Swift 4.2

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

and you have to write

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

You can figure out such terminology changes yourself by reading the documentation or by commenting out the entire method, retype the first few characters and use code completion.

Answer 2

I'm following also the same tutorial, the updated code looks like this:

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {      // The info dictionary may contain multiple representations of the image. You want to use the original.     guard let selectedImage = info[.originalImage] 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) }