[Readable Coding Practice] Image Caching

One of the best ways to reuse image data that you have already downloaded from network is image caching.

 

By applying image caching, you can prevent slow app performance such as lagging. 

 

class GFAvatarImageView: UIImageView {

    static let cache         = NSCache<NSString, UIImage>()
    
 }

func downloadImage(from urlString: String) {
        
        let cacheKey = NSString(string: urlString)
        
        if let image = GFAvatarImageView.cache.object(forKey: cacheKey){
            self.image = image
            return
        }
        
        guard let url = URL(string: urlString) else { return }
        URLSession.shared.dataTask(with: url) {[weak self] data, response, error in
            if let _ = error{ return }
            
            guard let response = response as? HTTPURLResponse, response.statusCode == 200 else { return }
            
            guard let data = data else { return }
            
            guard let image = UIImage(data: data) else { return }
            GFAvatarImageView.cache.setObject(image, forKey: cacheKey)
            DispatchQueue.main.async {
                self?.image = image
            }
            
        }.resume()
    }