how to use random string to let or var to url link - swift

Question

how to use random string to let or var to url link
i want to make random string for url
let url = URL(string:"https://www.pallive.net/random.json")
or see the code when i change values in the site linke in the app do not changed,but if i chnage name of url it change
the code not reload if i change the value in json and keep same file
if i want to reload i have to change the name of file how to do some thange
auotmatic change the url and keep the orginal in the ftp server
import Foundation
class Episode
{
var title: String?
var description: String?
var thumbnailURL: URL?
var url: URL?
var episodes = [Episode]()
init(title: String, description: String, thumbnailURL: URL, createdAt: String, author: String)
{
self.title = title
self.description = description
self.thumbnailURL = thumbnailURL
}
init(espDictionary: [String : AnyObject])
{
self.title = espDictionary["title"] as? String
// description = espDictionary["description"] as? String
thumbnailURL = URL(string: espDictionary["thumbnailURL"] as! String)
self.url = URL(string: espDictionary["link"] as! String)
}
static func downloadAllEpisodes(completion: #escaping ([Episode]) -> ()) {
var episodes = [Episode]()
let url = URL(string:"https://www.pallive.net/random.json")
URLSession.shared.dataTask(with: url!) { (data, response, error) in
if error != nil {
print(error)
completion(episodes)
}
else {
if let jsonData = data ,let jsonDictionary = NetworkService.parseJSONFromData(jsonData) {
let espDictionaries = jsonDictionary["episodes"] as! [[String : AnyObject]]
for espDictionary in espDictionaries {
let newEpisode = Episode(espDictionary: espDictionary)
episodes.append(newEpisode)
}
}
completion(episodes)
DispatchQueue.main.async(execute: {
completion(episodes)
})
}
}.resume()
}
func randomString(_ length: Int) -> String {
let letters : NSString = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
let len = UInt32(letters.length)
var randomString = ""
for _ in 0 ..< length {
let rand = arc4random_uniform(len)
var nextChar = letters.character(at: Int(rand))
randomString += NSString(characters: &nextChar, length: 1) as String
}
return randomString
}
}