ArgumentParser で Date を扱うときの例

date_formatter_with_argumentparser.swift

// https://forums.swift.org/t/support-for-date/34797/2?u=griffin-stewie

func parseDate(_ formatter: DateFormatter) -> (String) throws -> Date {
    { arg in
        guard let date = formatter.date(from: arg) else {
            throw ValidationError("Invalid date")
        }
        return date
    }
}

let shortFormatter = DateFormatter()
shortFormatter.dateStyle = .short

// .....later
@Argument(transform: parseDate(shortFormatter))
var date: Date