read write delete file

//files and ios sand box.....
import UIKit //you must import UIKit for getting all the extra commands

class FileWritter{
    //variebles
    //for createing string filename location
    var documentPath, fileName, fullPath:String!
    //for getting the ios file manager
    var fileManager = FileManager.default

    init() {
        fileSettings()
    }

    func fileSettings(){
        //name of file
        self.fileName = "zeev.txt"
        //for getting document path, we need to use our file manager....
        self.documentPath = NSSearchPathForDirectoriesInDomains(FileManager.SearchPathDirectory.documentDirectory, FileManager.SearchPathDomainMask.userDomainMask, true)[0]

        self.fullPath = "\(documentPath!)/\(fileName!)"
    }

    func test(){
        print (self.fullPath!)
    }

    func writeToFile(_ txt:String){
        var myData = readFromFile()
        myData += txt
        do{
            try myData.write(toFile: self.fullPath, atomically: true, encoding: String.Encoding.utf8)
            print ("wrote to file")
        } catch {
            print ("Error writting to file...")
        }
    }

    func readFromFile()->String{
        var temp = ""
        if fileManager.fileExists(atPath: fullPath){
            //read from file
            do{
                try temp = String(contentsOfFile: self.fullPath)
            } catch {

                //in string we can add ?? "with defualt value"
                print ("we can not read from file \(self.fileName ?? "filename currptted")")
            }
        } else {
            print ("there is no file in the system")
        }
        return temp
    }

    func deleteFile(){
        do{
            print ("file was deleted")
            try fileManager.removeItem(atPath: fullPath)
        } catch {
            print ("can not delete the file...")
        }
    }
}

var test = FileWritter()
test.deleteFile()
print (test.readFromFile())
test.writeToFile("let's do what we did last night \n")
print (test.readFromFile())
test.writeToFile("we will rule the world !!")
print (test.readFromFile())
test.deleteFile()
test.writeToFile("zeev")
print (test.readFromFile())