I have a data loading function that sometimes needs to update the ui via callback:
class Middleware {
...
func loadChannels(callback: #escaping (_ middleware: Middleware) -> Void) {
let url = URL(string: uri + "/entity.json")!
let task = URLSession.shared.dataTask(with: url) {
(data, response, error) in
guard let data = data, let _:URLResponse = response , error == nil else {
print("> loadChannels " + error.debugDescription)
return
}
let json = JSON(data: data)
if (json["entities"].array != nil) {
self.channels.removeAll()
for (_, json) in json["entities"] {
if let channel = Channel(json: json) {
self.channels += [channel]
}
}
if (callback != nil) {
callback!(self)
}
}
}
task.resume()
}
}
When I don't need the callback I'm calling it like this:
middleware.loadChannels(callback: { (middleware: Middleware) -> Void in })
Using
middleware.loadChannels(callback: nil)
doesn't work:
Nil is not compatible with expected argument type '(Middleware) -> Void'
Is there a less verbose way than my current version?
You need to make the callback optional:
func loadChannels(callback: ((_ middleware: Middleware) -> Void)?) {
}
Now you can pass nil to the callback parameter.
Related
New to swiftui and don't understand why the JSONDecoder() line in the first code throws
[SwiftUI] Publishing changes from background threads is not allowed; make sure to publish values from the main thread (via operators like receive(on:)) on model updates.
This to me is not updating ui so why is this showing?
do {
// pass the request type, bearer token, and email / password ( which are sent as POST body params )
let request = L.getRequest(requestType:"POST", token: token, email: self.username, password: self.psw)
L.fetchData(from: request) { result in
switch result {
case .success(let data):
// covert the binary data to a swift dictionary
do {
let response = try JSONDecoder().decode(WpJson.self, from: data)
for (key, title) in response.allowedReadings {
let vimeoId = Int( key )!
let vimeoUri = self.buildVimeoUri(vimeoId: key)
self.addReadingEntity(vimeoUri: vimeoUri, vimeoId: vimeoId, title: title)
}
self.writeToKeychain(jwt:response.jwt, displayName: response.displayName)
readings = self.fetchReadings()
}
catch {
self.error = error.localizedDescription
}
case .failure(let error):
self.error = error.localizedDescription
}
}
}
I tried wrapping a main queue around the do-catch in the L.fetchData(from: request) { result in but this did not help
DispatchQueue.main.async { [weak self] in
Here is the Login protocol, again without any ui work:
import Foundation
import SwiftUI
struct Login: Endpoint {
var url: URL?
init(url: URL?) {
self.url = url
}
}
protocol Endpoint {
var url: URL? { get set }
init(url: URL?)
}
extension Endpoint {
func getRequestUrl() -> URLRequest {
guard let requestUrl = url else { fatalError() }
// Prepare URL Request Object
return URLRequest(url: requestUrl)
}
func getRequest(requestType:String="POST", token:String, email:String="", password:String="") -> URLRequest {
var request = self.getRequestUrl()
request.httpMethod = "POST"
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
request.addValue("Bearer \(token)", forHTTPHeaderField: "Authorization")
if ( "" != email && "" != password && requestType == "POST") {
let parameters:[String:String?] = [
"email": email,
"password": password
]
// Run the request
do {
// pass dictionary to nsdata object and set it as request body
request.httpBody = try JSONSerialization.data(withJSONObject: parameters, options: .prettyPrinted)
} catch let error {
print(error.localizedDescription)
}
}
return request;
}
func fetchData(from request: URLRequest, completion: #escaping (Result<Data, NetworkError>) -> Void) {
URLSession.shared.dataTask(with: request) { data, response, error in
if let data = data {
completion(.success(data))
} else if error != nil {
// any sort of network failure
completion(.failure(.requestFailed))
} else {
// this ought not to be possible, yet here we are
completion(.failure(.unknown))
}
}.resume()
}
}
extension URLSession {
func dataTask(with request: URLRequest, completionHandler: #escaping (Result<(Data, HTTPURLResponse), Error>) -> Void) -> URLSessionDataTask {
return dataTask(with: request, completionHandler: { (data, urlResponse, error) in
if let error = error {
completionHandler(.failure(error))
} else if let data = data, let urlResponse = urlResponse as? HTTPURLResponse {
completionHandler(.success((data, urlResponse)))
}
})
}
}
Do you have any idea on how to fix this?
Wrap it right in place of assignment
catch {
DispatchQueue.main.async {
self.error = error.localizedDescription
}
}
case .failure(let error):
DispatchQueue.main.async {
self.error = error.localizedDescription
}
}
I am writing a Hacker News iOS application using SwiftUI/Combine. They have an API call for getting the ids of top posts and then you are supposed to request each story by itself. For this I have created storyIds(:) -> AnyPublisher<[Int], Error> and story(for:) -> AnyPublisher<Post, Error> for those calls.
Now I want to combine them into one function, getStories() which first download the identifiers and then goes through them fetching the stories one by one. I suppose you can use MergeMany or something else in the API for achieving this but I am not sure
The last thing I need is a function that combine these into stories() -> AnyPublisher<[Post], Error>. I found another question doing almost that. What I miss however, is a way to report progress of the task. I would like to update a counter for each fetched story to show the user how much is left of the download. How can I do this?
struct Agent {
struct Response<T> {
let value: T
let response: URLResponse
}
func run<T: Decodable>(_ request: URLRequest, _ decoder: JSONDecoder = JSONDecoder()) -> AnyPublisher<Response<T>, Error> {
return URLSession.shared
.dataTaskPublisher(for: request)
.tryMap { result -> Response<T> in
let value = try decoder.decode(T.self, from: result.data)
return Response(value: value, response: result.response)
}
.receive(on: DispatchQueue.main)
.eraseToAnyPublisher()
}
}
enum HackerNewsAPI {
static let agent = Agent()
static let base = URL(string: "https://hacker-news.firebaseio.com/v0/")!
}
extension HackerNewsAPI {
static func storyIds() -> AnyPublisher<[Int], Error> {
let request = URLRequest(url: base.appendingPathComponent("topstories.json"))
return agent.run(request)
.print()
.map(\.value)
.eraseToAnyPublisher()
}
}
extension HackerNewsAPI {
static func story(for id: Int) -> AnyPublisher<Post, Error> {
let request = URLRequest(url: base.appendingPathComponent("item/\(id).json"))
return agent.run(request)
.map(\.value)
.eraseToAnyPublisher()
}
}
extension HackerNewsAPI {
static func stories() -> AnyPublisher<[Post], Error> {
HackerNewsAPI.storyIds()
.flatMap { storyIDs -> AnyPublisher<[Post], Error> in
let stories = storyIDs.map { story(for: $0) }
return Publishers.MergeMany(stories)
.collect()
.eraseToAnyPublisher()
}
.eraseToAnyPublisher()
}
}
I expect something like the below code would work.
You end up with a count publisher that emits the number of articles that have been downloaded so far and a array publisher that emits the entire array of Posts after they have all been downloaded.
func getStories() -> (count: AnyPublisher<Int, Error>, stories: AnyPublisher<[Post], Error>) {
let posts = HackerNewsAPI.storyIds()
.map { $0.map { HackerNewsAPI.story(for: $0) } }
.flatMap { Publishers.Sequence(sequence: $0) }
.flatMap { $0 }
.share()
let count = posts
.scan(0) { count, _ in
return count + 1
}
let array = posts
.reduce([Post]()) { current, post in
current + [post]
}
return (count.eraseToAnyPublisher(), array.eraseToAnyPublisher())
}
I'm trying to migrate an extension to Alamofire.Request but am getting the error Cannot call value of non-function type 'HTTPURLResponse?'.
I know the compiler thinks I'm referring to the member response and not the function.
I've already replaced Request.JSONResponseSerializer with DataRequest.jsonResponseSerializer.
Can anyone see what I'm missing?
extension Alamofire.Request {
public func responseSwiftyJSON(_ queue: DispatchQueue? = nil, options: JSONSerialization.ReadingOptions = .allowFragments, completionHandler: #escaping (NSURLRequest, HTTPURLResponse?, SwiftyJSON.JSON, Error?) -> Void) -> Self {
return response(responseSerializer: Alamofire.DataRequest.jsonResponseSerializer(options: options)) { response in
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
var responseJSON: JSON
if response.result.isFailure {
responseJSON = JSON.null
} else {
responseJSON = SwiftyJSON.JSON(response.result.value!)
}
dispatch_async(queue ?? dispatch_get_main_queue(), {
completionHandler(self.request!, self.response, responseJSON, response.result.error)
})
}
}
}
}
I'm not sure if this is compatible with older versions, but I suggest you rewrite your extensions as this:
extension DataRequest {
public func responseSwiftyJSON(queue: DispatchQueue? = nil, options: JSONSerialization.ReadingOptions = .allowFragments, completionHandler: #escaping (URLRequest?, HTTPURLResponse?, SwiftyJSON.JSON, Error?) -> Void) -> Self {
return responseJSON(queue: queue, options: options) {
let responseJSON: JSON
switch result {
case let .success(json): responseJSON = JSON(json)
case .failure: responseJSON = JSON.null
}
completionHandler(request, response, responseJSON, error)
}
}
}
I am trying to access a url which can return either audio/image/video. I have created a helper class as below :
class LoadAsyncMedia{
static func getDataFromUrl(url: URL, completion: #escaping (_ data: Data?, _ response: URLResponse?, _ error: Error?) -> Void) {
URLSession.shared.dataTask(with: url) {
(data, response, error) in
completion(data, response, error)
}.resume()
}
static func downloadMedia(url: URL) {
print("Download Started \(url)")
getDataFromUrl(url: url) { (data, response, error) in
guard let data = data, error == nil else { return }
print(response?.suggestedFilename ?? url.lastPathComponent)
print("Download Finished")
print( response!)
print( data)
}
}
}
Below is call i m using to fetch the image first but i dont know how to convert the response into string then convert it into respective media.
LoadAsyncMedia.downloadMedia(url: URL(string: "http://htmlcolorcodes.com/assets/images/html-color-codes-color-tutorials-hero-00e10b1f.jpg")!)
I'm using Alamofire to send a login request to an HTTP server. It returns a JSON response. My problem is that the mainline code finishes before the .responseJSON. How do I wait until the response is returned before returning from the function?
var ret: Bool = true
Alamofire.request(
URL(string: "http://localhost:8081/login/iPhone")!,
method: .post,
parameters: ["email":"test#test.test", "password":"test", "uuid":String(describing: UIDevice.current.identifierForVendor!.uuidString)],
headers: [:])
.validate()
.responseJSON{(response) -> Void in
do {
guard response.result.isSuccess else {
throw FieldError.fetchError(responseError: response.result.error)
}
guard let value = response.result.value as? [String: Any],
let status = value["status"] as? String,
let message = value["message"] as? String else {
throw FieldError.messageFormatError
}
switch status {
case "Login suggess":
break
default:
throw FieldError.fieldServerError(status: status, message: message)
}
} catch {
ret = false
debugPrint(error)
}
}
return ret
You can always use global
typealias DownloadComplete = () -> ()
next in func with you're json
func yourFunc(completed: #escaping DownloadComplete)
and after download use
completed()