What is nonnull in objective C?

Question

Can someone elaborate why is nonnull introduced in iOS 9 ?

For example, the NSArray method + (instancetype)array; is now + (

Answer 1

nonnull is a keyword to tell the compiler that the return value (or parameter, or property) will never be nil. This was introduced in a previous version of Xcode to enable better inter operability between Obj-C and Swift's optional types.

You can learn more about it on the official Swift blog