> On Mar 31, 2016, at 3:54 PM, Guilherme Torres Castro via swift-evolution
> <[email protected]> wrote:
> Example:
> if !myList?.isEmpty { print("Ok") }
Swift originally had Optionals be boolean evaluable. Unfortunately, nil does
not always mean false, and assuming so by default can mask issues. I believe
there may have also been an issue with types being promoted to optional and
then evaluated as true.
One option here is to use a new custom prefix operator to indicate you desire
optional == false behavior. I chose “??” in the code below:
prefix operator ?? {}
prefix func ??(arg:Bool?) -> Bool {
return arg ?? false
}
let data:[String:Bool?] = ["nil": nil, "true": true, "false": false]
for (key, value) in data {
if ??value {
print(key)
}
} # prints true
I don’t think a negated form is as clear, since this is a shortcut for two
checks. However, I wrote one for completeness:
prefix operator ‽‽ {}
prefix func ‽‽(arg:Bool?) -> Bool {
return !(arg ?? false)
}
-DW_______________________________________________
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