Unwrap Or Throw (or Die!)
? Unwrap an optional or throw an error if nil (or crash the program).
Not invented here. The idea for unwrap or die and unwrap or throw has been around in the Swift community for years. You can read all about it in the references below.
Read more: Unwrap Or Throw (or Die)
This library provides different facilities to unwrap an
Swift provides a way to go from a throwing function to an optional
try?but it doesn’t have an easy way to do the reverse operation.
throw is not an expression so we can’t use it on the right side of the coalescing operator
raise function supplies this functionality. It’s a very simple function that throws the given error, but it makes it possible to use it in places where an expression is needed.
try someWork() ?? raise(YourError())
An overload of
?? is provided to remove the need for the
raise function. If you prefer to be succinct instead of explicit, you can just use an error on the right of the operator and it will just work.
try someWork() ?? YourError()
If you don’t like to abuse the coalescing operator to throw errors, you can instead use a method variant.
The library comes with a default error:
UnwrapError. So you can call the method without specifying a custom error.
☠️ Unwrap or die
Despite the name of the library, you can also crash the program instead of throwing an error.
You can use the same techniques as when throwing errors but using
fatalError("reason for crashing") instead:
try someWork() ?? raise(fatalError("reason for crashing"))
The compiler will show a warning on this line
Will never be executed so instead of using
raise you can directly
fatalError on the right side of the
try someWork() ?? fatalError("reason for crashing")
Or if you prefer the method, you can also use it:
try someWork().unwrapOrThrow(fatalError("reason for crashing"))
This has the same result as force unwrapping
! but with a better error message to help you see the problems on the logs.
A barely use the unwrap or die since when I want to force unwrap I just do that and I don’t find the lack of proper message an issue most of the time.
That’s why I don’t need to introduce a facility to just pass a reason
Stringdirectly into the unwrap operation.
- Introducing an “Unwrap or Throw” operator
- Unwrap or Throw – Make the Safe Choice Easier
- [Pitch] Introducing the “Unwrap or Die” operator to the standard library
- SE-0217 – The “Unwrap or Die” operator