Modify controller to write some data to a log file every second - swift

Question

I'm a Rails developer but I need to modify the controller of an application to save some sensors data to an external file.
I have this controller that take some data and populate a TableView, and data are updated every time I push a button in my view.
import UIKit
class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
#IBOutlet var tableView: UITableView!
var currentNames: [Any] = [], voltageNames: [Any] = [], thermalNames: [Any] = []
var currentValues: [Any] = [], voltageValues: [Any] = [], thermalValues: [Any] = []
override func viewDidLoad() {
super.viewDidLoad()
currentNames = currentArray()
voltageNames = voltageArray()
thermalNames = thermalArray()
currentValues = returnCurrentValues()
voltageValues = returnVoltageValues()
thermalValues = returnThermalValues()
self.tableView.register(UITableViewCell.self, forCellReuseIdentifier: "cell")
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
switch (section) {
case 0:
return currentNames.count
case 1:
return voltageNames.count
case 2:
return thermalNames.count
default:
return 0;
}
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell:UITableViewCell = self.tableView.dequeueReusableCell(withIdentifier: "cell")!
let string: NSMutableString = ""
switch (indexPath.section) {
case 0:
// cell.textLabel.text =
let name = currentNames[indexPath.row] as! NSString
let number = currentValues[indexPath.row] as! NSNumber
string.appendFormat("%#: %.2lf", name, number.doubleValue)
case 1:
let name = voltageNames[indexPath.row] as! NSString
let number = voltageValues[indexPath.row] as! NSNumber
string.appendFormat("%#: %.2lf", name, number.doubleValue)
case 2:
let name = thermalNames[indexPath.row] as! NSString
let number = thermalValues[indexPath.row] as! NSNumber
string.appendFormat("%#: %.2lf", name, number.doubleValue)
default:
break;
}
cell.textLabel?.text = string as String?
return cell
}
func numberOfSections(in tableView: UITableView) -> Int {
return 3;
}
func tableView(_ tableView: UITableView, titleForFooterInSection section: Int) -> String? {
switch (section) {
case 0:
return "Current (A), \(currentNames.count) items"
case 1:
return "Voltage (V), \(voltageNames.count) items"
case 2:
return "Temperature (°C), \(thermalNames.count) items"
default:
return "";
}
}
#IBAction func reloadData(_ sender : AnyObject) {
currentValues = returnCurrentValues()
voltageValues = returnVoltageValues()
thermalValues = returnThermalValues()
tableView.reloadData()
}
}
I need to refresh data every second without pushing the button and I want to save this data in a log file.
I create a log.swift file
import Foundation
struct Log: TextOutputStream {
func write(_ string: String) {
let fm = FileManager.default
let log = fm.urls(for: .documentDirectory, in: .userDomainMask)[0].appendingPathComponent("log.txt")
if let handle = try? FileHandle(forWritingTo: log) {
handle.seekToEndOfFile()
handle.write(string.data(using: .utf8)!)
handle.closeFile()
} else {
try? string.data(using: .utf8)?.write(to: log)
}
}
}
var logger = Log()
I know that I can do something every second with
Timer.scheduledTimer(withTimeInterval: 1, repeats: true) {
}
But I don't understand where to put this.
I just need to save a log with thermalNames and thermalValues
Basically the cell I have in my tableView
let name = thermalNames[indexPath.row] as! NSString
let number = thermalValues[indexPath.row] as! NSNumber
string.appendFormat("%#: %.2lf", name, number.doubleValue)
Then I will parse the file with ruby to convert to a csv...

Answer 1

In order to do that you have to create two functions. One for the action you want to perform and the other one for timer itself
here are the functions:
#objc func save() {
//Your Saving action has to be here
}
You have to call this one in ViewDidLoad
func startTimerForShowScrollIndicator() {
self.timer = Timer.scheduledTimer(timeInterval: 0.01, target: self, selector: #selector(self.save), userInfo: nil, repeats: true)
}