What's difference between NSPhotoLibraryAddUsageDescription and NSPhotoLibraryUsageDescription?

Question

My app get crashed today while updating on Xcode9, testing on iOS11. After adding NSPhotoLibraryAddUsageDescription then it works, even i already had NSPh

Answer 1

Simple get from Apple Official Document

Just click on above image for ZOOM and read it.

For more information on:

• NSPhotoLibraryAddUsageDescription: If you want to save a photo/image to your Photo Library. For iOS11 and +

• NSPhotoLibraryUsageDescription: If you want to access your Photo Library. For iOS10 and +