FileRename.swift

func renameFile(oldName:String , newName : String){

        do {

            let originPath = (self.getDirectoryPath() as NSString).appendingPathComponent(oldName)
            let destinationPath = (self.getDirectoryPath() as NSString).appendingPathComponent(newName)

            try FileManager.default.moveItem(at: URL(fileURLWithPath: originPath), to: URL(fileURLWithPath: destinationPath))

        } catch {
            print(error)
        }

    }

    func getDirectoryPath() -> String {
        let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
        let documentsDirectory = paths[0]
        return documentsDirectory
    }