Dictionary causes index out of range error in Swift - swift

Question

Sorry if this is asked already but I haven't found a solution for it. I'm new to Swift so please bear with me. I can't figure out why I keep getting an error of Thread 1: Fatal Error: Index out of range. I've used the same method before in displaying a txt file to which I never got a problem with before so this is the first time. I'm trying to display coordinates as the text details with the date and time as text in the cells itself.
Date and Time
Latitude, Longitude
Something like the above (Imagine it in a cell)
The following is my code for the program
import UIKit
import MapKit
class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
//Array to store the list
var storeCoordinates = [String: String]()
var arrayClient = NSMutableArray()
var readings: [String] = [" "]
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
//Get path of where the file is
let path = Bundle.main.path(forResource: "gps_coords", ofType: "csv")
//Use filemanager to check if the file exist to avoid crashing if it doesn't exist
let fileMgr = FileManager.default
//Display the number of line counts we have
if fileMgr.fileExists(atPath: path!){
do {
let fulltext = try String(contentsOfFile: path!, encoding: String.Encoding.utf8)
readings = fulltext.components(separatedBy: "\n") as [String]
for i in 0..<readings.count{
let listData = readings[i].components(separatedBy: ";") as [String]
storeCoordinates["Latitude"] = "\(listData[0])"
storeCoordinates["Longitude"] = "\(listData[1])"
storeCoordinates["DateAndTime"] = "\(listData[2])"
arrayClient.add(storeCoordinates)
}
} catch let error as NSError {
print("Error: \(error)")
}
}
self.title = "Number of entries: \(arrayClient.count)"
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return arrayClient.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cellReuseIdentifier", for: indexPath)
let client = arrayClient[indexPath.row] as AnyObject
cell.textLabel?.text = "\(client.object(forKey: "DateAndTime")!)"
cell.detailTextLabel?.text = "\(client.object(forKey: "Latitude")!) \(client.object(forKey: "Longitude")!)"
return cell
}
func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
}
The error I had is on storeCoordinates["Latitude"] = "\(listData[0])"
Using breakpoints, it shows the Latitude value is not empty along with Longitude and DateAndTime but if I try to run the app in the simulator, it gives the error Thread 1: Fatal Error: Index out of range. So far no luck in trying to figure out how to fix this. If you could help me figure it out, it would mean a lot to me. Please and thank you.

Answer 1

I regard the unreliable CSV format as the origin of the issue.
This is a quick tutorial to use a better format (JSON) and a more robust data source.
Part 1: Convert CSV to JSON
Create a new Blank Playground (press ⌥⇧⌘N) platform macOS
Press ⌘0 to show the project navigator of the Playground.
⌥-drag the CSV file from the project navigator of the main project into the Resources folder of the Playground.
Paste the following code into the Playground, it's based on your code to parse the CSV. It converts the CSV to JSON and creates a file gps_coords.json on the desktop. You'll get a fatal error if any field is missing.
struct Coordinate : Encodable {
let latitude, longitude, dateAndTime : String
}
let url = Bundle.main.url(forResource: "gps_coords", withExtension: "csv")!
let fulltext = try! String(contentsOf: url, encoding: .utf8)
let lines = fulltext.components(separatedBy: .newlines)
let coordinates = lines.map { paragraph -> Coordinate in
let components = paragraph.components(separatedBy: ";")
if components.count != 3 { fatalError("Each line must contain all three fields")}
return Coordinate(latitude: components[0], longitude: components[1], dateAndTime: components[2])
}
do {
let data = try JSONEncoder().encode(coordinates)
let homeURL = URL(fileURLWithPath: NSHomeDirectory())
let destinationURL = homeURL.appendingPathComponent("Desktop/gps_coords.json")
try data.write(to: destinationURL)
} catch { print(error) }
Part 2: Implement the new file
Close the Playground. It's not needed anymore.
Drag the new file from the desktop into the project navigator (make sure Copy If Needed is checked).
Change the ViewController class to
import UIKit
import MapKit
struct Coordinate : Decodable {
let latitude, longitude, dateAndTime : String
}
class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
var arrayClient = [Coordinate]()
override func viewDidLoad() {
super.viewDidLoad()
let url = Bundle.main.url(forResource: "gps_coords", withExtension: "json")!
let data = try! Data(contentsOf: url)
arrayClient = try! JSONDecoder().decode([Coordinate].self, from: data)
self.title = "Number of entries: \(arrayClient.count)"
tableView.reloadData()
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return arrayClient.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cellReuseIdentifier", for: indexPath)
let client = arrayClient[indexPath.row]
cell.textLabel?.text = client.dateAndTime
cell.detailTextLabel?.text = client.latitude + " " + client.longitude
return cell
}
}
Note: The UITableView outlet is missing and I added the line to reload the data. Make also sure that delegate and datasource is connected in Interface Builder from the table view to the ViewController.
Delete the CSV file.
The new code uses a struct Coordinate as data source and decodes the JSON very conveniently with JSONDecoder. Please note the missing type casts and the cumbersome key subscription to get the values from the dictionary.

Answer 2

As in the comment, mentioned by #vadian, It is not possible that you didn't get 0th index. But you add some checks.
Update your code as following:
Some updates are -
Use swift based array [[String: String]] rather NSMutableArray
Initialize the storeCoordinates for each loop cycle and check if your listData have more than 3 items or not
class AViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
//Array to store the list
var arrayClient = [[String: String]]()
var readings: [String] = []
override func viewDidLoad() {
super.viewDidLoad()
//Get path of where the file is
let path = Bundle.main.path(forResource: "gps_coords", ofType: "csv")
//Use filemanager to check if the file exist to avoid crashing if it doesn't exist
let fileMgr = FileManager.default
//Display the number of line counts we have
if fileMgr.fileExists(atPath: path!){
do {
let fulltext = try String(contentsOfFile: path!, encoding: String.Encoding.utf8)
readings = fulltext.components(separatedBy: "\n") as [String]
for i in 0..<readings.count {
// Check if you can get data from `readings[i]`
let listData = readings[i].components(separatedBy: ";") as [String]
if listData.count == 3 {
var storeCoordinates = [String: String]()
storeCoordinates["Latitude"] = "\(listData[0])"
storeCoordinates["Longitude"] = "\(listData[1])"
storeCoordinates["DateAndTime"] = "\(listData[2])"
arrayClient.append(storeCoordinates)
}
}
} catch let error as NSError {
print("Error: \(error)")
}
}
self.title = "Number of entries: \(arrayClient.count)"
}
func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return arrayClient.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cellReuseIdentifier", for: indexPath)
let client = arrayClient[indexPath.row]
if let dateTime = client["DateAndTime"], let latitude = client["DateAndTime"], let longitude = client["DateAndTime"] {
cell.textLabel?.text = "\(dateTime)"
cell.detailTextLabel?.text = "\(latitude) \(longitude)"
}
return cell
}
}