         collectionView.register(ForecastCell.self, forCellWithReuseIdentifier: "forecast")
         self.addSubview(collectionView)
        
+        // add observer to response change theme notification
+        NotificationCenter.default.addObserver(self, selector: #selector(changeTheme), name: NSNotification.Name(rawValue: "ChangeThemeNotification"), object: nil)
+
     }
     
     override func layoutSubviews() {

        fatalError("init(coder:) has not been implemented")
    }
    
}

extension ThreeDaysForecastView : UICollectionViewDataSource {

class ThreeDaysForecastView: UIView {
    
    var collectionView: UICollectionView!
    var darkStyle = false
    
    var forecastDays: [ForecastDay]! = [] {
        didSet {
            collectionView.reloadData()
