#nullability

Missing in PHP7: Nullable return types

This is the fifth post in my Missing in PHP7 series. The previous one is about Collections. This is a short post, as there really is not much to explain or motivate.

Nullable return types

As of PHP7, we have return types at our disposal. Unfortunately, these have some annoying limits. One of them I described in my PHP Collectionsblog post. Another is the lack of nullable return types. This blog…

UIAlertAction’s init method takes a String? for “title” in Swift, but the documentation states “This parameter must not be nil”

Summary: The UIAlertAction documentation states that the title parameter in its initializer "must not be nil". However, this parameter is marked as optional when it could be marked as non-optional to enforce this requirement at compile time.

Steps to Reproduce: Pass nil title to UIAlertAction initializer Application Crashes with no compiler error despite requirement of non-nil titles.

Expected Results: UIAlertAction initializer's title parameter should not be optional to enforce this requirement.

Actual Results: UIAlertAction initializer allows title to be nil, causing a crash.

[NSArray arrayWithArray:] now requires a nonnull argument. This was traditionally used a lot in situations where you either have nil or an array, to make sure there’s always an array. Granted, I don’t see that explicitly documented, but it’s something I see a lot in code. (Same behaviour with NSDictionary and NSSet)

[...]

We used arrayWithArray: to 

a) make sure we return immutable data b) make sure we always return an object and never nil.

I’ll recommend making the signature nullable to keep that useful behavior.