My question is somewhat similar to 69959018, so I have made sure to clarify as much as I can
I'm trying to use the Steam Web API to create an app that grabs everyone on my friend list in the form of a JSON dictionary. I'm trying to use foundation instead of Alamofire in order to learn Foundation better.
So far, what I've done is the following in AppDelegate.swift:
class AppDelegate: NSObject, NSApplicationDelegate {
func applicationDidFinishLaunching(_ aNotification: Notification) {
var apiKey: String = "[REDACTED]"
var steamID: String = "[REDACTED]"
let getPlayerSummaries = URL(string: "http://api.steampowered.com/ISteamUser/GetPlayerSummaries/v0002/?key=\(apiKey)&steamids=\(steamID)")
let friendList = downloadPlayerSummaries(with: getPlayerSummaries)
print(friendList)
}
func applicationWillTerminate(_ aNotification: Notification) {
// Insert code here to tear down your application
}
func applicationSupportsSecureRestorableState(_ app: NSApplication) -> Bool {
return true
}
}
In another file I made called networkManager.swift, I have wrote this based on what I have found in the apple documentation for "Fetching Website Data into Memory" :
//
// networkManager.swift
// Who is online?
//
// Created by Dash Interwebs on 11/21/21.
//
import Foundation
func downloadPlayerSummaries(with: URL!) {
let url = with
if url == nil {
print("url is nil")
return
}
let task = URLSession.shared.dataTask(with: url!) { data, response, error in
if let error = error {
self.handleClientError(error)
return
}
guard let httpResponse = response as? HTTPURLResponse,
(200...299).contains(httpResponse.statusCode) else {
self.handleServerError(response)
return
}
}
}
task.resume()
}
After this however, self.handleClientError(error), and self.handleServerError(response) complain about being unable to find "self". I can't find anything about handleServerError or handleClientError. So where exactly is "self" in this context? I think that it might be URLSession but I'm not too sure.
You can refactor your code using a completion handler and using an enum that conforms to the Error protocol:
enum ApiError: Error {
case network(Error)
case genericError
case httpResponseError
}
func downloadPlayerSummaries(with url: URL?, completion: #escaping (_ success: Bool, _ error: ApiError?) -> Void) {
guard let url = url else { return }
let task = URLSession.shared.dataTask(with: url) { data, response, error in
if let error = error {
completion(false, .network(error))
return
}
guard let httpResponse = response as? HTTPURLResponse,
(200...299).contains(httpResponse.statusCode) else {
completion(false, .httpResponseError)
return
}
// then handle your data. The completion should also include the kind of data your want to return
}
task.resume()
}
I haven't tested. Let me know if it works.
Related
I have a service class that makes an api call and stores data into its property. Then my interactor class have a method where I want to make service class api call and when data will be stored - return it. I tried myself to handle this with completion handler and dispatch group, but (I suppose I just missing something) this didn't work. I would be very appreciated if you help me to deal with this problem. Thanks in advance!
Service class:
class PunkApiService{
var beers = [Beer]()
func loadList(at page: Int){
//MARK: - Checks is URL is valid + pagination
guard let url = URL(string: "https://api.punkapi.com/v2/beers?page=\(page)&per_page=25") else {
print("Invalid URL")
return
}
//MARK: - Creating URLSession DataTask
let task = URLSession.shared.dataTask(with: url){ data, response, error in
//MARK: - Handling no erros came
guard error == nil else {
print(error!)
return
}
//MARK: - Handling data came
guard let data = data else{
print("Failed to load data")
return
}
do{
let beers = try JSONDecoder().decode([Beer].self, from: data)
self.beers.append(contentsOf: beers)
}
catch{
print("Failed to decode data")
}
}
task.resume()
}
And Interactor class(without completion handler or dispatch group):
class BeersListInteractor:BeersListInteractorProtocol{
private var favoriteBeers = FavoriteBeers()
private var service = PunkApiService()
//MARK: - Load list of Beers
func loadList(at page: Int) -> [Beer]{
service.loadList(at: page)
return service.beers
}
Added: my attempt with completion handler
var beers: [Beer]
func loadList(at page: Int, completion: ()->()){
service.loadList(at: page)
completion()
}
func completion(){
beers.append(contentsOf: service.beers)
}
loadList(at: 1) {
completion()
}
This is what async/await pattern is for, described here. In your case both loadList functions are async, and the second one awaits for the first one:
class PunkApiService {
func loadList(at page: Int) async {
// change function to await for task result
let (data, error) = try await URLSession.shared.data(from: url)
let beers = try JSONDecoder().decode([Beer].self, from: data)
...
return beers
}
}
class BeersListInteractor: BeersListInteractorProtocol {
func loadList(at page: Int) async -> [Beer]{
let beers = await service.loadList(at: page)
return service.beers
}
}
See a good explanation here
I think that you were on the right path when attempting to use a completion block, just didn't do it correctly.
func loadList(at page: Int, completion: #escaping ((Error?, Bool, [Beer]?) -> Void)) {
//MARK: - Checks is URL is valid + pagination
guard let url = URL(string: "https://api.punkapi.com/v2/beers?page=\(page)&per_page=25") else {
print("Invalid URL")
completion(nil, false, nil)
return
}
//MARK: - Creating URLSession DataTask
let task = URLSession.shared.dataTask(with: url){ data, response, error in
//MARK: - Handling no erros came
if let error = error {
completion(error, false, nil)
print(error!)
return
}
//MARK: - Handling data came
guard let data = data, let beers = try? JSONDecoder().decode([Beer].self, from: data) else {
completion(nil, false, nil)
return
}
completion(nil, true, beers)
}
task.resume()
}
This is the loadList function, which now has a completion parameter that will have three parameters, respectively the optional Error, the Bool value representing success or failure of obtaining the data, and the actual [Beers] array, containing the data (if any was retrieved).
Here's how you would now call the function:
service.loadList(at: page) { error, success, beers in
if let error = error {
// Handle the error here
return
}
if success, let beers = beers {
// Data was correctly retrieved - and safely unwrapped for good measure, do what you need with it
// Example:
loader.stopLoading()
self.datasource = beers
self.tableView.reloadData()
}
}
Bear in mind the fact that the completion is being executed asynchronously, without stopping the execution of the rest of your app.
Also, you should decide wether you want to handle the error directly inside the loadList function or inside the closure, and possibly remove the Error parameter if you handle it inside the function.
The same goes for the other parameters: you can decide to only have a closure that only has a [Beer] parameter and only call the closure if the data is correctly retrieved and converted.
I'm totally new to swift and iOS programming so I'm a little lost on how to do this and even in what files I should be doing this too.
I'm trying to do a http post request to get calendar events and save them in the app to later use and display.
I made a model class with this code.
import UIKit
class Event {
var id: Int
var init_date: String
var end_date: String
var title: String
var description: String
var color_code: String
var all_day: Int
init?(id: Int, init_date: String, end_date: String, title: String, description: String, color_code: String, all_day: Int) {
//Initialization should fail if these are false
if id < 0 || init_date.isEmpty || end_date.isEmpty || title.isEmpty {
return nil
}
//Initialize stored properties
self.id = id
self.init_date = init_date
self.end_date = end_date
self.title = title
self.description = description
self.color_code = color_code
self.all_day = all_day
}
}
But now I don't know what the next step would be. I need this to be downloaded immediately once the app is opened for the first time and not when it's not being opened for the first time. Do I create a new method in the ViewController.swift for the download?
Right now I haven't added anything to the ViewController
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
}
What should I do next?
At this point you need to create a function that handles the POST request you are making.
Once completed, place this function inside your appDelegate main function didFinishLaunchingWithOptions. This is the function that executes on appStart
On a successful function call save the data (presumably json) into a Global Variable or whatever you need for you app.
TIP:
On you class
class Event: Codable {
}
make sure to add Codable like above
Below is an example of what your post request will look like
func myPostRequest(completionHandler: #escaping (Bool?, String?) -> Void){
guard let url = URL(string:"") else { return }
let parameters = ["": ""]
var request: URLRequest = URLRequest(url: url)
request.httpMethod = "POST"
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
request.setValue("", forHTTPHeaderField: "Authorization")
do {
request.httpBody = try JSONSerialization.data(withJSONObject: parameters, options: .prettyPrinted)
let task = URLSession.shared.dataTask(with: request) { data, response, error in
guard
error == nil
else {
print(error as Any)
return
}
if let httpResponse = response as? HTTPURLResponse {
if (httpResponse.statusCode == 200) {
if let data = data {
let json = try? JSONSerialization.jsonObject(with: data, options: []) as? [[String: Any]]
//print("^^^^^^^^^^^^^^",json)
for x in json ?? [] {
//here is where you will parse your data from the post request
}
completionHandler(true, nil)
return
}
} else {
completionHandler(false, "No Response From Server")
print("Failure response: STATUS CODE != 200")
}
} else {
completionHandler(false, "Database Connection Error")
print("Error \(error!)")
}
}
task.resume()
} catch let error {
completionHandler(false, "failure")
print("POSTERROR: \(error.localizedDescription)")
}
}
I use Alamofire, you can add it to your project via:
Pods
Swift Package Manager
When you add the framework you can use it:
import Alamofire
Then you need to make your class with the protocol Codable to pass the data to your class.
class Event: Codable { }
Then you need to call the url and store the response in a variable:
override func viewDidAppear(_ animated: Bool) {
AF.request("your API rest url").responseData { (resData) in
guard let data = resData.data else { return }//Check if the data is valid
do {
let decoder = JSONDecoder()//Initialize a Json decoder variable
let decodedData = try decoder.decode(Event.self, from: data)//Decode the response data to your decodable class
//Print the values
print(decodedData.headers)
print(decodedData.id)
print(decodedData.init_date)
print(decodedData.end_date)
} catch {
print(error.localizedDescription)
}
}
}
I have this Networking class that i declared in the Model .
class Networking {
func response (url : String ) {
guard let url = URL(string: url) else {return}
URLSession.shared.dataTask(with: url, completionHandler: urlPathCompletionHandler(data:response:error:)).resume()
}
func urlPathCompletionHandler (data : Data? , response: URLResponse? , error: Error? ) {
guard let data = data else {return }
do {
let jsondecoder = JSONDecoder()
}catch {
print("Error \(error)")
}
}
}
In the controller . I have an array of users i declared and i want the controller to call from the Model Networking class instead of doing the networking inside the controller. This is part of my controller:
var users = [Users]()
var networking : Networking()
#IBOutlet weak var tableview : UITableView!
override func viewDidLoad() {
super.viewDidLoad()
tableview.delegate = self
tableview.dataSource = self
}
func getFromModel() {
var vm = networking.response()
}
I want a way of calling the networking class and return an array of users that i can set to the users array above and use it to populate the table view . If i wanted to do that inside the controller it would easy but i am not sure how i can return an array of users from the Model Networking class .
You need to modify your Network class like this:
class Networking {
func response<T: Codable>(url: String, completion: ((T) -> Void)?) {
guard let url = URL(string: url) else {return}
URLSession.shared.dataTask(with: url, completionHandler: { (data, response, error) in
self.urlPathCompletionHandler(data: data, response: response, error: error, completion: completion)
}).resume()
}
func urlPathCompletionHandler<T: Codable>(data : Data? , response: URLResponse? , error: Error?, completion: ((T) -> Void)?) {
guard let data = data else { return }
do {
let jsondecoder = JSONDecoder()
// Pseudo Code to decode users
completion?(decodedObject)
} catch {
print("Error \(error)")
}
}
}
And call it like this:
func getFromModel() {
networking.response(url: <#T##String#>) { (users: [User]) in
self.users = users
}
}
OK, there are a few thoughts:
Your response method is performing an asynchronous network request, so you need to give it a completion handler parameter. So, I might suggest something like:
class Networking {
enum NetworkingError: Error {
case invalidURL
case failed(Data?, URLResponse?)
}
private let parsingQueue = DispatchQueue(label: Bundle.main.bundleIdentifier! + ".parsing")
// response method to handle network stuff
func responseData(_ string: String, completion: #escaping (Result<Data, Error>) -> Void) {
guard let url = URL(string: string) else {
completion(.failure(NetworkingError.invalidURL))
return
}
URLSession.shared.dataTask(with: url) { data, response, error in
DispatchQueue.main.async {
if let error = error {
completion(.failure(error))
return
}
guard
let responseData = data,
let httpResponse = response as? HTTPURLResponse,
200 ..< 300 ~= httpResponse.statusCode
else {
completion(.failure(NetworkingError.failed(data, response)))
return
}
completion(.success(responseData))
}
}.resume()
}
// response method to handle the JSON parsing
func response<T: Decodable>(of type: T.Type, from string: String, completion: #escaping (Result<T, Error>) -> Void) {
responseData(string) { result in
switch result {
case .failure(let error):
completion(.failure(error))
case .success(let data):
self.parsingQueue.async {
do {
let responseObject = try JSONDecoder().decode(T.self, from: data)
DispatchQueue.main.async {
completion(.success(responseObject))
}
} catch let parseError {
DispatchQueue.main.async {
completion(.failure(parseError))
}
}
}
}
}
}
}
This obviously assumes that you have some Codable types. For example, it’s common for an API to have some common structure in its responses:
struct ResponseObject<T: Decodable>: Decodable {
let code: Int
let message: String?
let data: T?
}
And maybe the User is like so:
struct User: Decodable {
let id: String
let name: String
}
Then getFromModel (perhaps better called getFromRepository or something like that) could parse it with:
networking.response(of: ResponseObject<[User]>.self, from: urlString) { result in
switch result {
case .failure(let error):
print(error)
case .success(let responseObject):
let users = responseObject.data
// do something with users
}
}
For what it’s worth, if you didn’t want to write your own networking code, you could use Alamofire, and then getFromModel would do:
AF.request(urlString).responseDecodable(of: ResponseObject<[User]>.self) { response in
switch response.result {
case .failure(let error):
print(error)
case .success(let responseObject):
let users = responseObject.data
}
}
Now, clearly the model types are likely to be different in your example, but you didn’t share what your JSON looked like, so I had to guess, but hopefully the above illustrates the general idea. Make a generic-based network API and give it a completion handler for its asynchronous responses.
I have some basics in Swift, and I'm now trying to learn iOS development. I'm currently working in a small app that will ask resource on an API I've made that returns json made from :
struct A : Codable {
let name: String
let age: Int
}
struct B : Codable {
let something: String
}
Both API and app have these structs defined. As I'm always querying the same API, I thought of wrapping the part that ask the API some resources and decode this so I have an instance of the struct to use in my callback. Here's this method :
static func getContent(urlRequest: URLRequest, decodable: Decodable, completion: #escaping (Codable?, ErrorEnum?)->Void) {
let config = URLSessionConfiguration.default
let session = URLSession(configuration: config)
let task = session.dataTask(with: urlRequest) {
data, response, error in
guard let data = data else {
completion(nil, .noData) // Handling errors in an enum
return
}
let decoder = JSONDecoder()
if let full = try? decoder.decode(decodable, from: data) {
completion(full, nil)
}
}
task.resume()
}
My problem concerns the decodable param. This shows an error and prevent me from compiling the app. After finding some resources on StackOverflow, I tried to change the parameters as
static func getContent(urlRequest: URLRequest, decodable: Decodable.Type, completion: #escaping (Codable?, ErrorEnum?)->Void)
I also tried to keep the parameter like this, and instead change inside the decode params
if let full = try? decoder.decode(decodable, from: data) {
completion(full, nil)
}
but nothing seems to satisfy the compiler... And looking at decode method inside Swift source code didn't help me that much as it requires T.Type where T is Decodable
My wish is to be able to use this as follow :
static func getA() {
guard let url = URL(string: "http://localhost/a") else { return }
let urlRequest = URLRequest(url: url)
getContent(urlRequest: urlRequest, decodable: A.self) {
a, error in
guard a = a else { return }
print(a.name!)
}
}
Do you have any idea how I could achieve this ? I also don't really know how to call this type of parameters or what to search on google that can lead me to the answer (lack of vocabulary).
Thank you !
try this just add a generic .Type of Codable and use its type as a parameter to pass foo.self
static func getContent<T: Codable>(urlRequest: URLRequest, decodable: T.Type, completion: #escaping (T?, ErrorEnum?)->Void) {
let config = URLSessionConfiguration.default
let session = URLSession(configuration: config)
let task = session.dataTask(with: urlRequest) {
data, response, error in
guard let data = data else {
completion(nil, .noData) // Handling errors in an enum
return
}
let decoder = JSONDecoder()
if let full = try? decoder.decode(decodable, from: data) {
completion(full, nil)
}
}
task.resume()
}
You can use this:
func genericRequest<T: Decodable>(_ request: URLRequest, completion: #escaping APIGenericRequestCompletion<T>) {
Alamofire.request(request).responseData { (response) in
guard let data = response.data else {
completion(nil)
return
}
do {
let decodedObject = try JSONDecoder().decode(T.self, from: data)
completion(decodedObject)
} catch {
completion(nil)
}
}
}
where APIGenericRequestCompletion is:
typealias APIGenericRequestCompletion<T: Decodable> = (_ result: T?) -> Void
Then you use it as:
genericRequest(request) { (decodableObjectResponse) in
// your code here
}
I am currently working my way through he Treehouse IOS Swift course, and we are building a weather app. I've gotten to a point where I keep getting an error that my class isn't conforming to my protocol, but I can't figure out why.
Here is my protocol declaration:
public protocol APIClient {
var configuration: URLSessionConfiguration { get }
var session: URLSession { get }
func JSONTaskWithRequest(request: URLRequest, completion: JSONTaskCompletion) -> JSONTask
func fetch<T: JSONDecodable>(request: URLRequest, parse: (JSON) -> T?, completion: (APIResult<T>) -> Void)
}
And then I have a protocol extension where I have default implementations of my two methods declared in the protocol, and one of the methods is calling the other method, as you can see below.
public extension APIClient {
func JSONTaskWithRequest(request: URLRequest, completion: #escaping JSONTaskCompletion) -> JSONTask {
let task = session.dataTask(with: request) { data, response, error in
guard let HTTPResponse = response as? HTTPURLResponse else {
let userInfo = [
NSLocalizedDescriptionKey: NSLocalizedString("Missing HTTP Response", comment: "")
]
let error = NSError(domain: BPSnetworkingErrorDomain, code: MissingHTTPReponseError, userInfo: userInfo)
completion(nil, response as! HTTPURLResponse, error)
return
}
if data == nil {
if let error = error {
completion(nil, response as! HTTPURLResponse, error as NSError?)
}
} else {
switch HTTPResponse.statusCode {
case 200:
do {
let JSON = try JSONSerialization.jsonObject(with: data!, options: []) as? [String: AnyObject]
completion(JSON, HTTPResponse, nil)
} catch let error as NSError {
completion(nil, HTTPResponse, error)
}
default: print("Received HTTP Response \(HTTPResponse.statusCode) - not handled")
}
}
}
return task
}
public func fetch<T>(request: URLRequest, parse: #escaping (JSON) -> T?, completion: #escaping (APIResult<T>) -> Void) {
let task = JSONTaskWithRequest(request: request) { json, response, error in
DispatchQueue.main.async {
guard let json = json else {
if let error = error {
completion(.Failure(error))
} else {
let error = "Something is really wrong. There was no JSON object created, but there was no error either."
completion(.Failure(error as! Error))
}
return
}
if let value = parse(json) {
completion(.Success(value))
} else {
let error = NSError(domain: BPSnetworkingErrorDomain, code: unexpectedResponseError, userInfo: nil)
completion(.Failure(error))
}
}
}
task.resume()
}
}
Then I have my class declaration where I am getting my non conformity error.
final class ForecastAPIClient: APIClient {
let configuration: URLSessionConfiguration
lazy var session: URLSession = {
return URLSession(configuration: self.configuration)
}()
private let token: String
init(config: URLSessionConfiguration, APIKey: String) {
self.configuration = config
self.token = APIKey
}
convenience init(APIKey: String) {
self.init(config: URLSessionConfiguration.default, APIKey: APIKey)
}
func fetchCurrentWeather(coordinate: Coordinate, completion: #escaping (APIResult<CurrentWeather>) -> Void) {
let request = Forecast.Current(token: self.token, coordinate: coordinate).request
fetch(request: request, parse: { (JSON) -> CurrentWeather? in
if let currentWeatherDictionary = JSON["currently"] as? [String: AnyObject] {
return CurrentWeather(JSON: currentWeatherDictionary)
} else {
return nil
}
}, completion: completion)
}
}
I've done a lot of reading around for several hours trying to figure out what is going on here. From what I understand, I shouldn't need to define those two methods in my class since they have default implementations in the protocol extension. I came across the issue of public/internal types and things like that, that someone else was having here on StackExchange with their extensions, (as you an see by my labeling things public and what not), but that didn't seem to help in my case. The only way I've been able to get the error to go away, is by commenting out those method declarations in the original protocol declaration. Which seems to indicate to me that either the class, or the protocol, or something isn't seeing the extension for some reason, however, if I command click on the fetch method call in the class declaration, it takes me to the definition of it in the extension. I haven't been able to find a solution, or even someone who is doing this similar thing, there are several people on Treehouse that seem to be having this same issue as well.
Also, I download the teachers code, and converted it to Swift 3, and it was getting the same error as well, so maybe it's an issues with having a different version of Xcode the what he used when he made the video?
I feel like I'm kind of grasping at straws a little bit, but I really am eager to get this figured out, so any possible help would be so much appreciated.
Thank you!
I used Xcode's playground to test and play around with your code. I took your code (protocol declaration, protocol extension, and class declaration) and heavily simplified the JSONTaskWithRequest() and fetch() functions. The code compiled with no "non conformity error." Here is the code I used:
//: Playground :
import UIKit
// protocol declaration
public protocol APIClient {
var configuration: URLSessionConfiguration { get }
var session: URLSession { get }
func JSONTaskWithRequest()
func fetch()
}
// protocol extension
public extension APIClient {
func JSONTaskWithRequest() {
print("JSONTaskWithRequest here")
}
func fetch() {
print("fetch here")
}
}
// class declaration
final class ForecastAPIClient: APIClient {
let configuration: URLSessionConfiguration
lazy var session: URLSession = {
return URLSession(configuration: self.configuration)
}()
private let token: String
init(config: URLSessionConfiguration, APIKey: String) {
self.configuration = config
self.token = APIKey
}
}
I suspect that there is a bug in JSONTaskWithRequest and/or fetch. I suggest you isolate either function to figure out which one is giving you the error. Then debug from there.
Also, just another suspicion. In the extension's JSONTaskWithRequest function implementation, you have:
let task = session.dataTask(with: request) {...}
return task
JSONTaskWithRequest is required to return a JSONTask. Maybe you need to downcast task:
return task as! JSONTask
I couldn't use your provided code because things like JSONTaskCompletion and JSONDecodable aren't recognized by Swift. Are you using a third party JSON swift library?