Swift main loop for updating a view - ios

Question

I'm new to Swift and trying to implement a simple test Single-View app: Upon running, it should keep appending text lines in a UITextView automatically.
However, all I get is a blank screen with the following code:
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var m_logView: UITextView!
private let m_log = Log()
override func viewDidLoad() {
super.viewDidLoad()
addLog(msg: "Hello World!")
while true {
m_log.requestLog{ [weak self] (data: String) in
self?.consumeLog(log: data)
}
}
}
func consumeLog(log: String) {
addLog(msg: log)
}
func addLog(msg: String) {
m_logView.text += msg + "\n"
}
}
class Log {
func requestLog(consume: (_ log: String) -> Void) {
let log = "Data from wherever"
consume(log)
}
}
I suspected that I'm trying to update the UITextView at a wrong place. The above code simply blocks the viewDidLoad() from completing itself and showing the UITextView.
So I found viewDidAppear, but this time it gets stuck there and shows only "Hello World!" in the view.
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var m_logView: UITextView!
private let m_log = Log()
override func viewDidLoad() {
super.viewDidLoad()
addLog(msg: "Hello World!")
}
override func viewDidAppear(_ animated: Bool) {
while true {
m_log.requestLog{ [weak self] (data: String) in
self?.consumeLog(log: data)
}
}
}
func consumeLog(log: String) {
addLog(msg: log)
}
func addLog(msg: String) {
m_logView.text += msg + "\n"
}
}
class Log {
func requestLog(consume: (_ log: String) -> Void) {
let log = "Data from wherever"
consume(log)
}
}
Most iOS MVC tutorials I found teach how to implement the user interactions, but stay away from how to update the view by programmtically changing the model from the backend.
I'm probably looking for a callback/delegate where I can refresh UITextView linked with its data model whenever the data changes, but where is it?

Answer 1

The while loop is completely inappropriate because it causes a deadlock.
Use a Timer which works asynchronously
Replace
while true {
m_log.requestLog{ [weak self] (data: String) in
self?.consumeLog(log: data)
}
}
with
Timer.scheduledTimer(withTimeInterval: 0.01, repeats: true) { [weak self] _ in
m_log.requestLog{ data in
self?.consumeLog(log: data)
}
}
And you might update the UI explicitly on the main thread
func addLog(msg: String) {
DispatchQueue.main.async {
m_logView.text += msg + "\n"
}
}
Note:
According to the Swift naming convention name variables lowerCamelCased for example mLogView