[swift-evolution] Proposal: Deprecate optionals in string interpolation
val1984 at gmail.com
Thu May 19 01:52:41 CDT 2016
From what I understand of this thread, the argument here is that directly using an optional in a string interpolation is almost never what you really want to do (except mainly for debugging purposes) but you wouldn't see this mistake until much later at runtime.
And I feel like one of Swift goals is to enable us, imperfect human creatures, to detect as many problems or mistakes as possible long before runtime.
> On 19 mai 2016, at 00:56, Dan Appel via swift-evolution <swift-evolution at swift.org> wrote:
> Optional(foo) better depicts the actual type (it's an options string, after all). If you're not happy with it, just use the nil coalescing operator such as "\(foo ?? "")". This is from the same series of proposals as implicit casting - there are reasons it's done the way it is.
>> On Wed, May 18, 2016 at 3:49 PM Jacob Bandes-Storch via swift-evolution <swift-evolution at swift.org> wrote:
>> +1, personally I have taken to using `x+"str"+y` instead of `"\(x)str\(y)"`, if x/y are strings, so I can get a compile-time error if I do this accidentally.
>> But I do see the appeal of being able to print("the data: \(data)") for simple use cases. Didn't someone earlier propose some modifiers/labels like "\(describing: x)" ?
>>> On Wed, May 18, 2016 at 11:50 AM, 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.
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