> On 15 Aug 2016, at 08:02, Justin Jia via swift-evolution
> <[email protected]> wrote:
>
> Hi!
>
> I don’t know if this has came up before. I tried to search though the mailing
> list but didn’t find any related threads.
>
> This is purely a syntactic thing (which I know it’s the lowest priority for
> Swift 4), but I think it’s an important one.
>
> Let’s say we have a struct with a function:
>
> ```
> struct Foo {
> func bar(x: Int)
> }
> ```
>
> We can use optionals:
>
> ```
> let foo: Foo? = nil
> let x = 1
> foo!.bar(x: x) // Able to compile, but will cause runtime error
> foo?.bar(x: x) // Able to compile, and won't cause runtime error
> ```
>
> However:
>
> ```
> let foo = Foo()
> let x: Int? = nil
> foo.bar(x: x!) // Able to compile, but will cause runtime error
> foo.bar(x: x?) // Won't compile
> ```
>
> I propose that we should allow `foo.bar(x: x?)`, which should be equivalent
> to:
>
> ```
> if let x = x {
> foo.bar(x: x)
> }
> ```
>
> What do you think?
I like the intent behind this, but personally I think it's not clear enough.
For me, putting the statement in a conditional as you've shown is the better
solution, as it's a lot clearer exactly what's going on. Putting a question
mark on a variable makes it look like something specific to that variable,
rather than preventing the entire statement from executing.
There may be some alternatives though, for example, what about a shorthand for
the conditional like so:
if let x? { foo.bar(x: x) }
if x? { foo.bar(x: x) } // even shorter?
But in general, I think it's best to be explicit about the entire statement
being optional, which the conditional does but a postfix on a variable doesn't
to the same degree._______________________________________________
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