How to Omit Missing Fields from Date String (day, month, year)? - swift

Question

I have a DateFormatter where dateStyle is set to .long like so:
private let formatter: DateFormatter = {
let formatter = DateFormatter()
formatter.dateStyle = .long
return formatter
}()
In my application, I make requests to an API and can receive some info about dates in the response body. In response, it'll look like this for example:
struct StartDate {
let day: Int?
let month: Int?
let year: Int?
}
As all the fields are optional, some fields may or may not be present. For example, I may have a year and month, but not a day. Or maybe I only have the year. A demonstration of why this is a problem:
let date = Calendar.current.date(from: DateComponents(year: 2020, month: 12))!
print(formatter.string(from: date))
We have the year and month, but not the day. I may expect it to look like December 2020, December, 2020 or even December ?, 2020. However, it decides to replace the missing day with a 1. I can't use that because it's misleading to the user. How could I solve this problem?

Answer 1

Maybe a bit straight-forward but still. You can try something like this:
struct StartDate {
let day: Int?
let month: Int?
let year: Int?
var string: String {
get {
let daySymbols = day == nil ? "??" : String(day!)
let monthSymbols = month == nil ? "??" : DateFormatter().monthSymbols[month! - 1]
let yearSymbols = year == nil ? "??" : String(year!)
return "\(daySymbols) \(monthSymbols) \(yearSymbols)"
}
}
}
print(StartDate(day: nil, month: 10, year: 2020).string)
//prints '?? October 2020'
print(StartDate(day: 21, month: nil, year: 2020).string)
//prints '21 ?? 2020'
print(StartDate(day: 21, month: 9, year: nil).string)
//prints '21 September ??'