Just to remember

Sorting-Array.swift

import UIKit

// [^] Negated set - Match any character that is not in the set.
// @ Character - Matches "@" character (char code 64).
// * Quantifier - Match 0 or more of pending token.
// $ End - Matches the end of the string, or the end of a line if the multiline flag (m) is enabled. This matches a position, not a character.

func matchesRegex(_ regex: String, in text: String) -> String {
    do {
        let regex = try NSRegularExpression(pattern: regex)
        let nsString = text as NSString
        let results = regex.matches(in: text, range: NSRange(location: 0, length: nsString.length))
        return results.map { nsString.substring(with: $0.range)}.first ?? ""
    } catch let error {
        print("invalid regex: \(error.localizedDescription)")
        return ""
    }
}

let arr = ["004-STO05-Nature.mp4 @ 04 Nature", "003-STO05-Pictogram.mp4 @ 03 Pictogram", "007-STO05-Retail.jpg @ 07 Retail", "001-STO05-CHEMICAL.mp4 @ 01 Chemical", "006-STO05-Transportation.jpg @ 06 Transportation", "002-STO05-SQUARECITY.mp4 @ 02 Square City", "008-STO05-SPATIAL.mp4 @ 08 Spatial", "005-STO05-CityScape.jpg @ 05 CityScape"]
var dict = [String: String]()

for str in arr {
    let matched = matchesRegex("[^@]*$", in: str)
    if !matched.isEmpty {
        dict[str] = matched.trimmingCharacters(in: .whitespaces)
    }
}

let sorted = dict.sorted{ $0.value > $1.value }.map{ $0.key }
print(sorted)

// OR

let sortedInline = arr.sorted(by: { $0.components(separatedBy: "@").last ?? "" > $1.components(separatedBy: "@").last ?? "" })
print(sortedInline)