Swift Network Image

NetworkImageView.swift

// You can use this class to download images for UICollectionViewCells or UITableViewCells with no worries about cell reusage

import UIKit

class NetworkImageView: UIImageView {
    
    private var imageDownloadTask: URLSessionDataTask?
    private var activityIndicator: UIActivityIndicatorView?
    
    public func imageFromURL(url: URL) {
        
        imageDownloadTask?.cancel() // cancel the previous task if exists
        activityIndicator?.removeFromSuperview() // if activity indicator exists remove it from superview
        
        if self.image == nil {
            activityIndicator = UIActivityIndicatorView(style: .medium) // We are sure that activity indicator exists after this line so force unwrapping is safe
            activityIndicator!.translatesAutoresizingMaskIntoConstraints = false
            self.addSubview(activityIndicator!)
            activityIndicator!.centerXAnchor.constraint(equalTo: self.centerXAnchor).isActive = true
            activityIndicator!.centerYAnchor.constraint(equalTo: self.centerYAnchor).isActive = true
            activityIndicator!.startAnimating()
        }

        imageDownloadTask = URLSession.shared.dataTask(with: url, completionHandler: { [weak self] (data, response, error) -> Void in

            if let error = error {
                print(error)
                return
            }
            DispatchQueue.main.async(execute: { () -> Void in
                let image = UIImage(data: data!)
                self?.activityIndicator?.removeFromSuperview()
                self?.image = image
            })

        })
        imageDownloadTask?.resume()
    }
}