Alamofire could not update class property data - ios

Question

Hi i am trying to use alamofire to download json weather data. Here is my code, the working version:
class WeatherModel {
private var _date: String?
private var _location: String?
private var _weatherType: String?
private var _temperature: Double?
func getWeatherInfoFromAPI(completed: #escaping ()-> ()) {
let url = URL(string: WEATHER_URL)!
Alamofire.request(url).responseJSON(completionHandler: { response in
// Test updating data
self._temperature = 25
self._weatherType = "Clear"
self._location = "Vietnam"
completed()
})
}
}
-> This way, i am able to update the property of the class.
Failing to update class property version of getWeatherInfoFromAPI func:
func getWeatherInfoFromAPI(completed: #escaping ()-> ()) {
let url = URL(string: WEATHER_URL)!
Alamofire.request(url).responseJSON{ response in
// Test updating data
self._temperature = 25
self._weatherType = "Clear"
self._location = "Vietnam"
}
completed()
}
So, i dont know what is the difference between them. Please help me to clarify between 2 ways here.
Alamofire.request(url).responseJSON(completionHandler: { response in })
and
Alamofire.request(url).responseJSON{ response in }
What is the reason that my code does not work? Since i see the Alamofire docs also use like the second way! I am thinking about thread difference between them
Also, how do i know what thread the code is running in responseJSON?
Thanks, i appreciate your time and help!

Answer 1

Those two ways are functionally identical, the second one just uses Swift's trailing closure syntax.
What do you do in completed()? Because in first example, you are calling it upon completion of network call, and in second case you are calling it immediately after you start the network call - the call is not completed yet. You should call if in Alamofire callback, like in first example. In second example, if you're inspecting those properties inside completed, then it's no wonder they're not updated yet.