Swift async load image

**Swift 5.0+ updated Code :

extension UIImageView {

    
        func imageFromServerURL(_ URLString: String, placeHolder: UIImage?) {

        self.image = nil
        //If imageurl's imagename has space then this line going to work for this
        let imageServerUrl = URLString.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed) ?? ""
        

        if let url = URL(string: imageServerUrl) {
            URLSession.shared.dataTask(with: url, completionHandler: { (data, response, error) in

                //print("RESPONSE FROM API: \(response)")
                if error != nil {
                    print("ERROR LOADING IMAGES FROM URL: \(error)")
                    DispatchQueue.main.async {
                        self.image = placeHolder
                    }
                    return
                }
                DispatchQueue.main.async {
                    if let data = data {
                        if let downloadedImage = UIImage(data: data) {
                       
                            self.image = downloadedImage
                        }
                    }
                }
            }).resume()
        }
    }
}

Now wherever you required just do this to load image from server url :

1. Using swift 5.0 + updated code using placeholder image : UIImageView.imageFromServerURL(URLString:"here server url",placeHolder: placeholder image in uiimage format)

Simple !

Use extension in Swift3. To resolve Network problem i recommend you use NSCache:

import UIKit

let imageCache = NSCache<NSString, AnyObject>()

extension UIImageView {
    func loadImageUsingCache(withUrl urlString : String) {
        let url = URL(string: urlString)
        self.image = nil

        // check cached image
        if let cachedImage = imageCache.object(forKey: urlString as NSString) as? UIImage {
            self.image = cachedImage
            return
        }

        // if not, download image from url
        URLSession.shared.dataTask(with: url!, completionHandler: { (data, response, error) in
            if error != nil {
                print(error!)
                return
            }

            DispatchQueue.main.async {
                if let image = UIImage(data: data!) {
                    imageCache.setObject(image, forKey: urlString as NSString)
                    self.image = image
                }
            }

        }).resume()
    }
}

Hope it help!