[swift-evolution] !? operator for ternary conditional unwrapping

[Martin R]

Isn't that exactly what the nil-coalescing operator ?? does?

    func query(name: String?) -> String {
        return "{ param: \(name ?? "null") }"
    }

If you use the JSONSerialization class from the Foundation library then `nil` is bridged to `NSNull` and translated to "null" automatically (see SE-0140).

Regards,
Martin

> Am 08.02.2017 um 15:04 schrieb Maxim Veksler via swift-evolution <swift-evolution at swift.org>:
> 
> Hello, 
> 
> Let's assume I have an optional "name" parameter, based on the optional status of the parameters I would like to compose string with either the unwrapped value of name, or the string "null". The use case for is syntactic sugar to compose a GraphQL queries.
> 
> A (sampled) illustration of the code that currently solves it looks as following:
> 
> func query(name: String?) {
>   let variables_name = name != nil ? "\"\(name!)\"" : "null"
>   return "{ param: \(variables_name) }"
> }
> 
> Based on optional status the following output is expected
> 
> let name = "Max"
> query(name: name) 
> // { param: "Max" }
> 
> let name: String? = nil
> query(name: name)
> // { param: null }
> 
> I think it might be useful to have an conditional unwrap operator !? that would enable syntax sugar uch as the following built into the language:
> 
> func query(name: String?) {
>   return "{ param: \(name !? "\"\(name)\"": "null") }"
> }
> 
> This expression is expected to produce same output as the examples above. It means check the Optional state of name: String?, in case it has a value, unwrap it and make the unwrapped value accessible under the same name to the true condition part of the expression, otherwise return the false condition part of the expression.
> 
> The effectively removes the need to have the "if != nil" and the forced unwrap syntactical code, and IMHO improves code readability and expressiveness.
> 
> I'm wondering what the community thinks of the displayed use case, and proposed solution?
> 
> 
> -m
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution