.swift

struct JsonDownloader
{
    public func downloadContentsOfUrl(
        url: URL,
        onUrlRetrieved: @escaping (_ url: URL, (UIImage) -> Void) -> Void,
        onImageDownloaded: @escaping (_ image: UIImage) -> Void
    ) -> Void {
        // This async call will be thrown onto a thread and then this function will return immediately
        DispatchQueue.global(qos: .background).async {
            let json = try! Data(contentsOf: url)
            
            let jsonData = try! JSONSerialization.jsonObject(with: json, options: []) as! [String: Any]
            
            // Calling our first callback, and passing in the second, violating LoD
            onUrlRetrieved(URL(string: jsonData["image_url"] as! String)!, onImageDownloaded)
        }
    }
}