.swift

struct JsonDownloader
{
    public func downloadContentsOfUrl(_ url: URL) -> Promise<String> {
        return Promise { resolve, reject in
            let jsonData = try! Data(contentsOf: url)

            let jsonData = try! JSONSerialization.jsonObject(with: response, options: []) as! [String: Any]

            return resolve(url: jsonData['image_url'])
        }
    }
}