Extension to String to Extract Hash Tags (source: https://learnappmaking.com/regular-expressions-swift-string/)

string_extract_hashtags_extension.swift

extension String {
    func hashtags() -> [String] {
        guard let regex = try? NSRegularExpression(pattern: "#[a-z0-9]+", options: .caseInsensitive) else { 
            return [] 
        }
     
        let string = self as NSString

        return regex.matches(in: self, options: [], range: NSRange(location: 0, length: string.length)).map {
            string.substring(with: $0.range).replacingOccurrences(of: "#", with: "").lowercased()
        }
    }
}