let cache = try! TwoLevelCache<UIImage>("effective-png-cache")
cache.downloader = { (key, callback) in
    let url = URL(string: key)!
    URLSession.shared.dataTask(with: url) { data, response, error in
        callback(data)
    }.resume()
}
cache.deserializer = { (data) in
    return UIImage(data: data)
}
cache.serializer = { (object) in
    return UIImagePNGRepresentation(object)
}

cache.findObject(forKey: "https://nzigen.com/static/img/common/logo.png") { (image, status) in
    DispatchQueue.main.sync {
        imageView.image = image
    }
}

.memory  // Level 1 (NSCache)
.file  // Level 2 (NSCachesDirectory)
.downloader  // Cache miss (your device has downloaded the object)
.error  // All caches return nil and downloading data has been failed

cache.removeAllObjects()
cache.removeObject(forKey: "https://nzigen.com/static/img/common/logo.png")