Any Swift nerds? need help pulling data out of datatask()

[AlexGoesHigh]

Basically i can't figure out how to get the data of a datatask() call outside the closure, googling and in a lot of tutorials all they do is process the data (aka pass the data to a json decoder when the data is a json request) and assign that to property of the class, and in most cases an empty array of the object obtained from the request, but everytime i do that i always get nil errors of some kind, right now i'm trying to pass the json object into an array but every time i call the array i get index out of bounds, basically is not in the array.

 

i've already tried passing the data to another closure that gets handled when i call the function where i'm dealing with datatask, i've also tried making the request and handling it in a different object and now i don't know what else to try, i guess this forum may be not the best place to ask about programing on apple stuff but i guess i should try, i'd take any help even if just pointing to other places for help.

 

Spoiler

the code:

ViewController:

import UIKit

class ViewController: UIViewController {
    
    private var weather = [Weather]()
    
    @IBOutlet weak var table: UITableView!
    
    @IBOutlet weak var latitude: UILabel!
    @IBOutlet weak var longitude: UILabel!
    
    @IBOutlet weak var temperature: UILabel!
    @IBOutlet weak var windSpeed: UILabel!
    @IBOutlet weak var windDirection: UILabel!
    @IBOutlet weak var elevation: UILabel!
    
    
    //MARK: Class private
    
    private func getDataFromAPI(weather: @escaping (Result<Weather, Error>) -> Void) {
        let weatherURL = "https://api.open-meteo.com/v1/forecast?latitude=40.42&longitude=-3.70&hourly=temperature_2m,relativehumidity_2m,apparent_temperature,precipitation_probability,precipitation,rain,surface_pressure,cloudcover,visibility&current_weather=true&forecast_days=1"
        
        if let url = URL(string: weatherURL) {
            URLSession.shared.dataTask(with: url) { (data, response, error) in
                if let error = error {
                    print(error)
                }
                
                if let response = response {
                    print(response)
                }
                
                guard let data = data else { return }
                weather(Result { try JSONDecoder().decode(Weather.self, from: data)})
            }.resume()
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        getDataFromAPI(){ weather in
            switch weather {
            case .success( let gotWeather):
                self.weather[0] = gotWeather
                print(gotWeather)
                DispatchQueue.main.async {
                    self.table.reloadData()
                }
            case .failure( let error):
                print(error)
            }
        }
        // Do any additional setup after loading the view.
        table.delegate = self
        table.dataSource = self

        self.latitude.text = String(weather[0].latitude)
        self.longitude.text = String(weather[0].longitude)

        self.temperature.text! += String(weather[0].currentWeather.temperature)
        self.windSpeed.text! += String(weather[0].currentWeather.windspeed)
        self.windDirection.text! += String(weather[0].currentWeather.windDirection)
        self.elevation.text! += String(weather[0].elevation)
        
        }
}

extension ViewController: UITableViewDelegate, UITableViewDataSource {
    
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return weather[0].hourly.time.count
    }
    
    func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! WeatherTableViewCell
        
        cell.loadCell(weather: weather[0], arrayIndex: indexPath.item)
        
        return cell
    }
}

 

if need i can add the json decodable that i've made and the table cell class but i've already checked the data is parsed correctly and the build fails before reaching the table anyways.

[Blqckqut]

27 minutes ago, AlexGoesHigh said:

 

hi alex, hows ur G2?

[elpiop]

Your weather array is empty. Initializing it using [Weather]() creates an array with 0 elements. So trying to index into it will crash your app. 

 

instead of `self.weather[0] = gotWeather` (which will give you an index out of range exception), you can use either:

self.weather.insert(gotWeather, at: 0)

// or this

self.weather.append(gotWeather)

 

[aiwiguna]

Your issue is concurrency, you are accessing the weather array in viewDidLoad, numberOfRowsInSection and cellForRowAt function before the datatask finish because the data task is running in background thread.

Here some change that you need to do to fixed it

override func viewDidLoad() {
        super.viewDidLoad()
        getDataFromAPI(){ weather in
            switch weather {
            case .success( let gotWeather):
                self.weather.append(gotWeather)
                print(gotWeather)
                DispatchQueue.main.async {
                    self.latitude.text = String(weather[0].latitude)
                    self.longitude.text = String(weather[0].longitude)

                    self.temperature.text! += String(weather[0].currentWeather.temperature)
                    self.windSpeed.text! += String(weather[0].currentWeather.windspeed)
                    self.windDirection.text! += String(weather[0].currentWeather.windDirection)
                    self.elevation.text! += String(weather[0].elevation)
                    self.table.reloadData()
                }
            case .failure( let error):
                print(error)
            }
        }
        // Do any additional setup after loading the view.
        table.delegate = self
        table.dataSource = self
        }
}

extension ViewController: UITableViewDelegate, UITableViewDataSource {
    
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    	if weather.count != 0 {
        	return weather[0].hourly.time.count
        } else {
        	return 0
        }
    }
    
    func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! WeatherTableViewCell
        if weather.count != 0 {
        	cell.loadCell(weather: weather[0], arrayIndex: indexPath.item)
        }
        return cell
    }
}

 

[AlexGoesHigh]

5 hours ago, aiwiguna said:

Your issue is concurrency, you are accessing the weather array in viewDidLoad, numberOfRowsInSection and cellForRowAt function before the datatask finish because the data task is running in background thread.

Here some change that you need to do to fixed it

override func viewDidLoad() {
        super.viewDidLoad()
        getDataFromAPI(){ weather in
            switch weather {
            case .success( let gotWeather):
                self.weather.append(gotWeather)
                print(gotWeather)
                DispatchQueue.main.async {
                    self.latitude.text = String(weather[0].latitude)
                    self.longitude.text = String(weather[0].longitude)

                    self.temperature.text! += String(weather[0].currentWeather.temperature)
                    self.windSpeed.text! += String(weather[0].currentWeather.windspeed)
                    self.windDirection.text! += String(weather[0].currentWeather.windDirection)
                    self.elevation.text! += String(weather[0].elevation)
                    self.table.reloadData()
                }
            case .failure( let error):
                print(error)
            }
        }
        // Do any additional setup after loading the view.
        table.delegate = self
        table.dataSource = self
        }
}

extension ViewController: UITableViewDelegate, UITableViewDataSource {
    
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    	if weather.count != 0 {
        	return weather[0].hourly.time.count
        } else {
        	return 0
        }
    }
    
    func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! WeatherTableViewCell
        if weather.count != 0 {
        	cell.loadCell(weather: weather[0], arrayIndex: indexPath.item)
        }
        return cell
    }
}

 

THANK YOU!

 

I knew I was dealing with concurrency but i'm new to this so i didn't figured out those conditionals on the table functions for it to do something while its fetching the data, also the labels on dispatch queue.