For a given Int you can get the appropriate suffx

integer-suffixes.swift

extension Int {
    
    public func suffix() -> String {
        let absSelf = abs(self)
        
        switch (absSelf % 100) {
            
        case 11...13:
            return "th"
        default:
            switch (absSelf % 10) {
            case 1:
                return "st"
            case 2:
                return "nd"
            case 3:
                return "rd"
            default:
                return "th"
            }
        }
    }
}