cellForItemAt function not being called

Question

The function isn't being called and displaying no data. My code is below and I'm not getting any errors printed in the console. I set a break point on the function and it does not catch.

I was previously getting an index out of bounds crash but changed some code and now the collection view does not populate.

import UIKit
import CoreLocation

class ForecastController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {

    @IBOutlet weak var collectionView: UICollectionView!

    let rainArray : [Int] = [1,2,3,4,5,6,7,8,9,10]
    let cloudyArray : [Int] = [26,27,28,29,30]
    let snowArray : [Int] = [13,14,15,16]
    let sunnyArray : [Int] = [31,32,33,34]
    let stormArray : [Int] = [41,42,43,44,45,46,47]

    var Forecast : [Forecast] = []

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return Forecast.count
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize.init(width: 165, height: 200)
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: ForecastCell.reuseId, for: indexPath) as? ForecastCell else {
                return collectionView.dequeueReusableCell(withReuseIdentifier: "blank", for: indexPath)
        }
        let data = Forecast[indexPath.item]
        cell.summary.text = data.text
        cell.highLow.text = "\(data.high) | \(data.low)"
        cell.dayLabel.text = data.day

        if self.rainArray.contains(data.code) == true {
            cell.weatherIcon.image = UIImage(named: "Rain.png")
        } else if self.snowArray.contains(data.code) == true {
            cell.weatherIcon.image = UIImage(named: "snow.png")
        } else if self.cloudyArray.contains(data.code) == true {
            cell.weatherIcon.image = UIImage(named: "cloudy.png")
        } else if self.sunnyArray.contains(data.code) == true {
            cell.weatherIcon.image = UIImage(named: "sunny.png")
        } else if self.stormArray.contains(data.code) == true {
            cell.weatherIcon.image = UIImage(named: "storm.png")
        } else {
            cell.weatherIcon.image = UIImage(named: "cloudy.png")
        }
        return cell
    }

    func getWeather() {
        YahooWeatherAPI.shared.weather(lat: "\(currentLat!)", lon: "\(currentLong!)", failure: { (error) in
            print(error.localizedDescription)
            print("Error pulling weather data")
        }, success: { (response) in
            let data = response.data
            do {
                let weather = try JSONDecoder().decode(Weather.self, from: data)
                for x in weather.forecasts {
                    // populate collection view
                    self.Forecast = [x]
                }
            } catch {
                print(error)
            }
        }, responseFormat: .json, unit: .imperial)
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        collectionView.dataSource = self
        collectionView.delegate = self

        getWeather()
        // Do any additional setup after loading the view.
    }
}
class ForecastCell: UICollectionViewCell {

    @IBOutlet weak var weatherIcon: UIImageView!
    @IBOutlet weak var dayLabel: UILabel!
    @IBOutlet weak var summary: UILabel!
    @IBOutlet weak var highLow: UILabel!
    public static var reuseId : String = "forecastCell"

}

Answer 1

You should call reloadData() after you got data from Yahoo:

do {
    let weather = try JSONDecoder().decode(Weather.self, from: data)
    for x in weather.forecasts {
        // populate collection view
        self.Forecast = [x]
    }
    collectionView.reloadData()
} catch {
    print(error)
}

Your delegate doesn't know that data has changed so cellForItemAt isn't called.