You could always write something like this:
func query(name: String?) -> String {
let variables_name = String(format: name == nil ? "%@" : "\"%@\"", name ??
"null")
return "{ param: \(variables_name) }"
}
query(name: "Max") //=> "{ param: "Max" }"
query(name: nil) //=> "{ param: null }"
As far as I’m concerned, string interpolation in Swift does not allow nested
string literals (yet).
But a ternary operator that could potentially unwrap a list of optional values
would be neat.
Bikeshedding:
(optional1, optional2, optional1) ? { tupleWithUnwrappedOptionals in return R }
: { R }
// variadic generic parameter list
ternary func ?: <…T, R>(list: (…T?), lhs: ((…T) -> R), rhs: () -> R) -> R {
if let unwrappedList = // unwrap all optionals in `list` {
return lhs(unwrappedList)
} else {
return rhs()
}
}
--
Adrian Zubarev
Sent with Airmail
Am 8. Februar 2017 um 15:04:44, Maxim Veksler via swift-evolution
(swift-evolution@swift.org) schrieb:
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
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