Unused positional argument skipped in String formatting (Swift) - swift

Question

I want to format a string, in Swift, with two potential arguments (using Format specifiers). The string to format may have a place for only the first argument, only the second argument, or both arguments. If I use the first or both arguments it works, but if I use only the second argument, it does not work. For instance:
let title = "M."
let name = "David"
let greetingFormat = "Hello %1$# %2$#"
print(String(format: greetingFormat, title, name))
// OUTPUT> Hello M. David
// OK
If I use only the first argument in the String to format:
let greetingFormat = "Hello %1$#"
print(String(format: greetingFormat, title, name))
// OUTPUT> Hello M.
// OK
But when using only the second argument
let greetingFormat = "Hello %2$#"
print(String(format: greetingFormat, title, name))
// OUTPUT> Hello M.
// NOT THE EXPECTED RESULT!
In the last case I expected "Hello David". Is it a bug? How can I obtain the intended result for the last case where only the second argument is used?
Remarks:
Please note that this problem occurs in the context of localization (i.e. the string to format comes from a Localizable.strings file), so I don’t have the possibility to remove unused argument directly.
The question does not relate to person’s name formatting. This is just taken as a example.

Answer 1

I answer my own question but all credit to #Martin R that provides the relevant information in comments.
It is not a bug, String(format:) does not support omitting positional parameters.
It is a known behavior since ObjectiveC, see: stackoverflow.com/a/2946880/1187415
If you only have String arguments you can use multiple String substitutions with String.replacingOccurrences(of:, with:) instead of String(format:).
More precision on the last solution. The following will work in the case that only one argument is used and also if both arguments are used in the greetingFormat String:
greetingFormat.replacingOccurrences(
of: "%1$#", with: title)
.replacingOccurrences(
of: "%2$#", with: name)
Of course, with String.replacingOccurrences(of:, with:) you can choose other identifiers for the substitution than %1$# and %2$#.