[swift-evolution] Proposal: Deprecate optionals in string interpolation

Krystof Vasa kvasa at icloud.com
Thu May 19 12:06:48 CDT 2016

I'm wondering which scenario this is actually wanted behavior:

- strings that are for user interaction? Definitely not.
- logs? To be honest, the logs riddled with Optional(value) are pain to read. Following example:

key1: Optional("Value")
key2: nil


key1: Value
key2: nil

Which is more readable in the log?

I just don't see the benefit of the current behavior than perhaps in Xcode's playground where it displays the value on the right and perhaps a few minor cases - but definitely not 99% of the time.

This is IMHO not crippling interpolation, just asking for a non-nil values for it to be interpoled with.


> On May 19, 2016, at 6:07 PM, Jeremy Pereira via swift-evolution <swift-evolution at swift.org> wrote:
> -1
> This seems to me like crippling string interpolation just because sometimes we make mistakes. 99% of the time, if I interpolate an optional, it’s because I want it that way. I don’t want to have to put up with a warning or write the same boilerplate 99% of the time just to flag up the 1% more easily. Sorry.
>> On 18 May 2016, at 19:50, Krystof Vasa via swift-evolution <swift-evolution at swift.org> wrote:
>> The string interpolation is one of the strong sides of Swift, but also one of its weaknesses. 
>> It has happened to me more than once that I've used the interpolation with an optional by mistake and the result is then far from the expected result. 
>> This happened mostly before Swift 2.0's guard expression, but has happened since as well.
>> The user will seldomly want to really get the output "Optional(something)", but is almost always expecting just "something". I believe this should be addressed by a warning to force the user to check the expression to prevent unwanted results. If you indeed want the output of an optional, it's almost always better to use the ?? operator and supply a null value placeholder, e.g. "\(myOptional ?? "<<none>>")", or use myOptional.debugDescription - which is a valid expression that will always return a non-optional value to force the current behavior.
>> Krystof
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