Swift Network Stack

GenericStack.swift

enum Result<T> {
    case success(T)
    case error(Error)
}

struct ToDo : Codable {
    var id: Int
    var userId: Int
    var title:String
    var completed:Bool
}

typealias callback<T> = (Result<T>) -> Void

class Network {
    
    let host = URL(string:"https://jsonplaceholder.typicode.com/todos")!
    
    func getStuff(id:Int, callback: @escaping callback<ToDo>) -> URLSessionTask {
        let urlRequest = URLRequest(url: host.appendingPathComponent("\(id)"))
                
        let session = URLSession(configuration: URLSessionConfiguration.default)
        let task = session.dataTask(with: urlRequest) { (data, response, error) -> Void in
            
            print(response!)
            
            if let e = error {
                callback(.error(e))
                return
            }
            
            // TODO should also ret an error to callback, oops!!
            guard let data = data else { return }
            
            do {
                let todo = try JSONDecoder().decode(ToDo.self, from: data)
                callback(.success(todo))
                return
                
            } catch {
                let err = NSError(domain: "CustomThing", code: 1, userInfo: .none)
                callback(.error(err))
            }
        }
        
        task.resume()
        return task
    }
}


let cb:callback<ToDo> = { result in
    switch result {        
    case .success(let todo):
        print("Got the TODO! \(todo)")
        
    case .error(let err):
        print("got an error: \(err)")
    }
}

let n = Network()

n.getStuff(id: 1, callback: cb)