ping through host array and show results in table - arrays

Question

I am trying to ping an array containing different hosts. In each loop, I am saving an image depending on whether the ping was successful or not (checkImg, errorImg). Afterwards, I want to present the information (hostname and img) in a table.
The following code does work somehow but it is not stable. Sometimes I receive the following warning:
Thread 1: Fatal error: Index out of range In line: imgServer.image =
UIImage(named: statusImagesMain[indexPath.row])
So I suppose the ping loop for the different hosts did not get completed before serverStatusTable.reloadData() is executed.
Do you have any idea what I can do to overcome this problem?
swift 4
import UIKit
class ServerVC: SimplePingDelegate, UITableViewDelegate, UITableViewDataSource {
#IBOutlet weak var serverStatusTable: UITableView!
let imageError = UIImage(named: "error")
let imageCheck = UIImage(named: "check")
var pings = ["www.apple.com", "www.appleidontknowwhy.de", "www.apple.com", "www.apple.com"]
var hosts = [String]() // hostnames which get pinged
var componentTextArray = [String]() // project names
var statusImagesTemporary = [String]() // temporary store images
var statusImagesMain = [String]() // array filled with temporary stored images
var serverStatusMain = [String]() // server status string (connected, error)
var serverStatusTemporary = [String]() // temporary server status
override func viewDidLoad() {
super.viewDidLoad()
serverStatusTable.dataSource = self
serverStatusTable.delegate = self
statusImagesMain = ["error", "error", "error", "error"]
componentTextArray = ["Project 1", "Project 2", "Project 3", "Project 4"]
serverStatusMain = ["no data", "no data", "no data", "no data"]
hosts = pings
pingNext()
serverStatusTable.reloadData()
}
override func viewDidAppear(_ animated: Bool) {
// initial ping host process when loading the view
startHostRequest()
}
#IBAction func refreshBtnAction(_ sender: Any) {
// manual ping host process when clicking the button "refresh"
startHostRequest()
}
func startHostRequest () {
print("refresh server status")
pingNext()
// clear array before each host ping process in order for the array to keep only four items
statusImagesMain.removeAll()
serverStatusMain.removeAll()
for statusImageTemporary in statusImagesTemporary {
statusImagesMain.append(statusImageTemporary)
}
for i in serverStatusTemporary {
serverStatusMain.append(i)
}
serverStatusTable.reloadData()
}
func pingNext() {
guard pings.count > 0 else {
return
}
let ping = pings.removeFirst()
PlainPing.ping(ping, withTimeout: 1.0, completionBlock: { (timeElapsed:Double?, error:Error?) in
if let latency = timeElapsed {
print("\(ping) latency (ms): \(latency)")
// fill temporary arrays with img and serverStatus text for successful connection
self.statusImagesTemporary.append("check")
self.serverStatusTemporary.append("Running ")
}
if let error = error {
print("error: \(error.localizedDescription)")
// fill temporary arrays with img and serverStatus text for failed connection attempt
self.statusImagesTemporary.append("error")
self.serverStatusTemporary.append("Error ")
}
self.pingNext()
})
}
// fill table with host data
func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return componentTextArray.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = serverStatusTable.dequeueReusableCell(withIdentifier: "serverStatusCell", for: indexPath)
let lblServerStatus : UILabel = cell.contentView.viewWithTag(8) as! UILabel
let imgServer : UIImageView = cell.contentView.viewWithTag(7) as! UIImageView
imgServer.image = UIImage(named: statusImagesMain[indexPath.row])
lblServerStatus.text = serverStatusMain[indexPath.row]
return cell
}
}

Answer 1

Your bug lies in startHostRequest() and tableView(_ tableView: UITableView, numberOfRowsInSection section: Int).
In startHostRequest() you copy statusImagesTemporary to statusImagesMain, and statusImageTemporary is empty at the start, and it finishes with .reloadData(). tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) returns componentTextArray.count which is always 4. When these two are put together once startHostRequest() is called the table is reloaded, instructed to have 4 rows, but there are 0 rows of data to fill in the rows.
Managing your UITableView can be simplified by using ALTableViewHelper [commercial - available on here
]. The UITableView’s cells are maintained for you - matched, in your case, to the contents of statusImagesTemporary:
class ServerVC: UIViewController, UITableViewDelegate {
#IBOutlet weak var serverStatusTable: UITableView!
#objc let imageError = UIImage(named: "error")
#objc let imageCheck = UIImage(named: "check")
var pings = ["www.apple.com", "www.appleidontknowwhy.de", "www.apple.com", "www.apple.com"]
var hosts = [String]() // hostnames which get pinged
#objc var componentTextArray = [String]() // project names
#objc var serverStatusMain = NSMutableArray() // not [String]() to allow changes to be observed
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
// do not set dataSource, but instead:
serverStatusTable.setHelperString(
"section\n" +
" body\n" +
" serverStatusCell * serverStatusMain\n" +
" $.viewWithTag:(8).text <~ #[1] == 'error' ? 'Error ' : 'Running '\n" +
" $.viewWithTag:(7).image <~ #[1] == 'error' ? imageError : imageCheck \n" +
" $.viewWithTag:(2).text <~ componentTextArray[#[0]]\n" +
"", context:self)
// # is the value from the array (serverStatusMain), and $ is the serverStatusCell for #
// The selector for UIView.viewWithTag() is 'viewWithTag:', which is why you see that in the helper string
// Short arrays were added below as the values in serverStatusMain. In each short array:
// [0] is the index into hosts[] and componentTextArray[]
// [1] is the result of the ping, ie "check" or "error"
// so #[0] is the index and #[1] is the result of the ping
serverStatusTable.delegate = self
componentTextArray = ["Project 1", "Project 2", "Project 3", "Project 4"]
hosts = pings
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
override func viewDidAppear(_ animated: Bool) {
// initial ping host process when loading the view
startHostRequest()
}
#IBAction func refreshBtnAction(_ sender: Any) {
// manual ping host process when clicking the button "refresh"
startHostRequest()
}
func startHostRequest () {
// I thought you might need this here so that the 2nd and later ‘starts’ do the whole list
pings = hosts
// This will empty your UITableView
serverStatusMain.removeAllObjects()
print("refresh server status")
pingNext()
}
func pingNext() {
guard pings.count > 0 else {
return
}
let ping = pings.removeFirst()
PlainPing.ping(ping, withTimeout: 1.0, completionBlock: { [weak self](timeElapsed:Double?, error:Error?) in
if let me = self {
if let latency = timeElapsed {
print("\(ping) latency (ms): \(latency)")
me.serverStatusMain.add([me.serverStatusMain.count, "check"])
}
if let error = error {
print("error: \(error.localizedDescription)")
me.serverStatusMain.add([me.serverStatusMain.count, "error"])
}
me.pingNext()
}
})
}
}
You can see the complete demo project including this code here.