Open Radar

 
Summary:
Applications that only require write-access to a user’s Photo Library appear to have no method for determining permissions programatically. In the past, applications could use +authorizationStatus on PHPhotoLibrary to determine permissions. In cases where permission had been denied, it was useful to explain that an application, such as a camera app, would not perform as expected unless permission was granted.

However, with the addition of NSPhotoLibraryAddUsageDescription in iOS 11, along with the new behavior of UIImageWriteToSavedPhotosAlbum() displaying a system dialog, it appears to be impossible for an application to check for write-only permissions to the Photos Library.

This causes a significant UX challenge in cases where the user launches the app, but is not looking at the screen when a photo is taken (like in camera apps with remote shutter control).

A sample application that attempts to demonstrate this issue is attached.

Steps to Reproduce:
1. Create an application that requires write-only access to the Photos Library. Include NSPhotoLibraryAddUsageDescription in the app’s Info.plist.

2. Use [PHPhotoLibrary authorizationStatus] to verify a freshly-installed application has a “not determined” authorization status.

3. Attempt to write an image to the user’s Photo Library with UIImageWriteToSavedPhotosAlbum(). Observe the system will display a permissions prompt.

4. Use [PHPhotoLibrary authorizationStatus] to observe the application still has a “not determined” authorization status, regardless of the user-provided permissions response.

Expected Results:
[PHPhotoLibrary authorizationStatus] should reflect the authorization status of applications requiring write-only access to Photos Library.

Actual Results:
[PHPhotoLibrary authorizationStatus] does not reflect authorization status if [PHPhotoLibrary requestAuthorization:] is never sent.

Version:
qua

Notes:
A few other notes related to this problem. If [PHPhotoLibrary requestAuthorization:] is sent without NSPhotoLibraryUsageDescription, the application crashes, even if NSPhotoLibraryAddUsageDescription is present.

However, if +requestAuthorization is used and NSPhotoLibraryAddUsageDescription is present, then read-write access is requested. Then, +authorizationStatus correctly reflects the status, but write-only access has not been achieved, which my be adequate for the application’s needs.