I got a getJSON Function with url parameter:
func getJsons(jsonUrl: String) {
guard let url = URL(string: jsonUrl) else { return }
URLSession.shared.dataTask(with: url:) { (data, response, err) in
if err != nil {
print("ERROR: \(err!.localizedDescription)")
let alertController = UIAlertController(title: "Error", message:
err!.localizedDescription, preferredStyle: UIAlertControllerStyle.alert)
alertController.addAction(UIAlertAction(title: "Dismiss", style: UIAlertActionStyle.default,handler: nil))
var topController:UIViewController = UIApplication.shared.keyWindow!.rootViewController!
while ((topController.presentedViewController) != nil) {
topController = topController.presentedViewController!;
}
topController.present(alertController, animated: true, completion: nil)
}
guard let data = data else { return }
do {
let test = try JSONDecoder().decode([ArticleStruct].self, from: data)
DispatchQueue.main.async {
self.myArticles = test
print(self.myArticles?.count ?? 0 )
self.myTableView.reloadData()
}
} catch let jsonErr {
print("Error:", jsonErr)
}
}.resume()
}
now i want to move the function to another class (network class).
what must I do to add a completionHandler to the function and how do I call it from other classes.
i want to return the json to the caller class.
My plan:
in MainActivity -> viewDidLoad: call network completionHandler(getJsons(192.168.178.100/getPicture.php))
on completion -> myJsonDataMainActivity = (json data from completionHandler)
-> MainActivity.TableView.reload
in otherClass -> call network completionHandler(getJsons(192.168.178.100/getData.php))
on completion -> myJsonDataOtherClass = (json data from completionHandler)
-> otherClass.TableView.reload
Thanks for your help!
You can use delegate.
myJsonDataOtherClass:
protocol NetworkDelegate {
func didFinish(result: Data)
}
class myJsonDataOtherClass {
var delegate: NetworkDelegate? = nil
...
func getJsons(jsonUrl: String) {
...
URLSession.shared.dataTask(with: url:) { (data, response, err) in
...
delegate?.didFinish(data)
}.resume()
}
}
and set delegate at MainActivity
class MainActivity: UIViewController, NetworkDelegate{
...
let jsonClass = myJsonDataOtherClass()
jsonClass.delegate = self
jsonClass.getJsons(jsonUrl:url)
func didFinish(result:Data) {
// process data
}
}
You should add a completion handler in your function and pass the JSON object.
func getJsons(jsonUrl: String, completion:#escaping (_ success: Bool,_ json: [String: Any]?) -> Void) {
...
completion(true, json)
}
Related
self.werteEintragen() should start after weatherManager.linkZusammenfuegen() is done. Right now I use DispatchQueue and let it wait two seconds. I cannot get it done with completion func because I dont know where to put the completion function.
This is my first Swift file:
struct DatenHolen {
let fussballUrl = "deleted="
func linkZusammenfuegen () {
let urlString = fussballUrl + String(Bundesliga1.number)
perfromRequest(urlString: urlString)
}
func perfromRequest(urlString: String)
{
if let url = URL(string: urlString) {
let session = URLSession(configuration: .default)
let task = session.dataTask(with: url) { (gettingInfo, response, error) in
if error != nil{
print(error!)
return
}
if let safeFile = gettingInfo {
self.parseJSON(datenEintragen: safeFile)
}
}
task.resume()
}
}
func parseJSON(datenEintragen: Data) {
let decoder = JSONDecoder()
do {
let decodedFile = try decoder.decode(JsonDaten.self, from: datenEintragen)
TeamOne = decodedFile.data[0].home_name
} catch {
print(error)
}
}
}
And this is my second Swift File as Viewcontroller.
class HauptBildschirm: UIViewController {
func werteEintragen() {
Tone.text = TeamOne
}
override func viewDidLoad() {
super.viewDidLoad()
weatherManager.linkZusammenfuegen()
DispatchQueue.main.asyncAfter(deadline: .now() + 2) { [unowned self] in
self.werteEintragen()
}
}
}
How can I implement this and where?
func firstTask(completion: (_ success: Bool) -> Void) {
// Do something
// Call completion, when finished, success or faliure
completion(true)
}
firstTask { (success) in
if success {
// do second task if success
secondTask()
}
}
You can have a completion handler which will notify when a function finishes, also you could pass any value through it. In your case, you need to know when a function finishes successfully.
Here is how you can do it:
func linkZusammenfuegen (completion: #escaping (_ successful: Bool) -> ()) {
let urlString = fussballUrl + String(Bundesliga1.number)
perfromRequest(urlString: urlString, completion: completion)
}
func perfromRequest(urlString: String, completion: #escaping (_ successful: Bool) -> ()) {
if let url = URL(string: urlString) {
let session = URLSession(configuration: .default)
let task = session.dataTask(with: url) { (gettingInfo, response, error) in
guard error == nil else {
print("Error: ", error!)
completion(false)
return
}
guard let safeFile = gettingInfo else {
print("Error: Getting Info is nil")
completion(false)
return
}
self.parseJSON(datenEintragen: safeFile)
completion(true)
}
task.resume()
} else {
//can't create URL
completion(false)
}
}
Now, in your second view controller, call this func like this:
override func viewDidLoad() {
super.viewDidLoad()
weatherManager.linkZusammenfuegen { [weak self] successful in
guard let self = self else { return }
DispatchQueue.main.async {
if successful {
self.werteEintragen()
} else {
//do something else
}
}
}
}
I highly recommend Google's Promises Framework:
https://github.com/google/promises/blob/master/g3doc/index.md
It is well explained and documented. The basic concept works like this:
import Foundation
import Promises
struct DataFromServer {
var name: String
//.. and more data fields
}
func fetchDataFromServer() -> Promise <DataFromServer> {
return Promise { fulfill, reject in
//Perform work
//This block will be executed asynchronously
//call fulfill() if your value is ready
//call reject() if an error occurred
fulfill(data)
}
}
func visualizeData(data: DataFromServer) {
// do something with data
}
func start() {
fetchDataFromServer
.then { dataFromServer in
visualizeData(data: dataFromServer)
}
}
The closure after "then" will always be executed after the previous Promise has been resolved, making it easy to fulfill asynchronous tasks in order.
This is especially helpful to avoid nested closures (pyramid of death), as you can chain promises instead.
I'am learning swift and I see an example here https://matteomanferdini.com/network-requests-rest-apis-ios-swift/ and Im trying to change the code for something that work for me.
this is how the original code looks
struct Wrapper<T: Decodable>: Decodable {
let items: [T]?
}
protocol NetworkRequest: AnyObject {
associatedtype ModelType
func decode(_ data: Data) -> ModelType?
func load(withCompletion completion: #escaping (ModelType?) -> Void)
}
extension NetworkRequest {
fileprivate func load(_ url: URLRequest, withCompletion completion: #escaping (ModelType?) -> Void) {
let session = URLSession(configuration: .default, delegate: nil, delegateQueue: .main)
let task = session.dataTask(with: url, completionHandler: { [weak self] (data: Data?, response: URLResponse?, error: Error?) -> Void in
if let error = error {
print("Error: \(error)")
}
guard let data = data else {
completion(nil)
return
}
completion(self?.decode(data))
})
task.resume()
}
}
class APIRequest<Resource: APIResource> {
let resource: Resource
init(resource: Resource) {
self.resource = resource
}
}
extension APIRequest: NetworkRequest {
func decode(_ data: Data) -> [Resource.ModelType]? {
let wrapper = try? JSONDecoder().decode(Wrapper<Resource.ModelType>.self, from: data)
return wrapper?.items
}
func load(withCompletion completion: #escaping ([Resource.ModelType]?) -> Void) {
load(resource.request, withCompletion: completion)
}
}
but what I need to change the structure Wrapper to
struct Wrapper<T: Decodable>: Decodable {
let items: [T]?
let response: Bool?
let message: String?
}
and return items, response and message not only items
In this case you don't need the protocol at all because you want to get the root object.
This is sufficient
struct Wrapper<T: Decodable>: Decodable {
let items: [T]
let response: Bool
let message: String
}
class NetworkRequest {
func load<T : Decodable>(_ request: URLRequest, withCompletion completion: #escaping (Result<Wrapper<T>,Error>) -> Void) {
let session = URLSession(configuration: .default, delegate: nil, delegateQueue: .main)
let task = session.dataTask(with: request) { data, _, error in
if let error = error {
completion(.failure(error))
} else {
completion( Result {try JSONDecoder().decode(Wrapper<T>.self, from: data!)})
}
}
task.resume()
}
}
The completion handler returns a Result object, on success the wrapper object and on failure all errors.
In the wrapper struct declare all properties non-optional to get error messages and change only those to optional which really can be nil.
I change the code like this
class NetworkRequest<Resource: APIResource> {
let resource: Resource
init(resource: Resource) {
self.resource = resource
}
func load(withCompletion completion: #escaping (Result<Wrapper<Resource.ModelType>,Error>) -> Void) {
let session = URLSession(configuration: .default, delegate: nil, delegateQueue: .main)
let task = session.dataTask(with: self.resource.request) { data, _, error in
if let error = error {
completion(.failure(error))
} else {
completion( Result {try JSONDecoder().decode(Wrapper<Resource.ModelType>.self, from: data!)})
}
}
task.resume()
}
}
struct LoginResource: APIResource {
typealias ModelType = Token
let methodPath = "/users/login/"
let method = "post"
var params: [String: Any]?
init(username: String, password: String) {
self.params = ["username":username, "password": password]
}
}
In my view:
func login() {
if user == "" || password == "" {
self.title_alert = "Info"
message_alert = "Test Alert"
show_alert = true
return
}
let loginRequest = NetworkRequest(resource: LoginResource(username:user,password:password))
loginRequest.load { result in
switch result {
case .failure(let error):
print(error)
case .success(let data):
print(data)
}
}
}
I don't know if this is the best way but works Thank you #vadian
I have a function that creates and returns Observable that downloads and decodes data using URLSession. I wanted to write unit test for this function but have no idea how to tackle it.
function:
func getRecipes(query: String, _ needsMoreData: Bool) -> Observable<[Recipes]> {
guard let url = URL(string: "https://api.spoonacular.com/recipes/search?\(query)&apiKey=myApiKey") else {
return Observable.just([])
}
return Observable.create { observer in
let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
guard let data = data else {
return
}
do {
if self.recipes == nil {
self.recipes = try self.decoder.decode(Recipes.self, from: data)
self.dataList = self.recipes.results
self.baseUrl = self.recipes.baseUrl
} else {
if needsMoreData {
self.recipes = try self.decoder.decode(Recipes.self, from: data)
self.dataList.append(contentsOf: self.recipes.results.suffix(50))
} else {
self.dataList = try self.decoder.decode(Recipes.self, from: data).results
}
}
observer.onCompleted()
} catch let error {
observer.onError(error)
}
}
task.resume()
return Disposables.create {
task.cancel()
}
}
.trackActivity(activityIndicator)
}
The obvious answer is to inject the dataTask instead of using the singleton inside your function. Something like this:
func getRecipes(query: String, _ needsMoreData: Bool, dataTask: #escaping (URL, #escaping (Data?, URLResponse?, Error?) -> Void) -> URLSessionDataTask) -> Observable<[Recipes]> {
guard let url = URL(string: "https://api.spoonacular.com/recipes/search?\(query)&apiKey=myApiKey") else {
return Observable.just([])
}
return Observable.create { observer in
let task = dataTask(url) { (data, response, error) in
// and so on...
You would call it in the main code like this:
getRecipes(query: "", false, dataTask: URLSession.shared.dataTask(with:completionHandler:))
In your test, you would need something like this:
func fakeDataTask(_ url: URL, _ completionHandler: #escaping (Data?, URLResponse?, Error?) -> Void) -> URLSessionDataTask {
XCTAssertEqual(url, expectedURL)
completionHandler(testData, nil, nil)
return URLSessionDataTask()
}
let result = getRecipes(query: "", false, dataTask: fakeDataTask)
Did you know that URLSession has Reactive extensions already created for it? The one I like best is: URLSession.shared.rx.data(request:) which returns an Observable which will emit an error if there are any problems getting the data. I suggest you use it.
I'm using this code to load an image from a URL: Loading/Downloading image from URL on Swift. That is working fine.
I've take the code out of the viewcontroller and put it into a class. Now the image only loads when I step through the code. I'm guessing this has something to do with the code running fine but everything finishes executing before the image has completely downloaded from the web.
What piece of this am I missing so the code waits for the image without holding up any other code executing in the viewcontroller?
class MyClass:NSObject {
private var myImage:UIImage = UIImage()
func getMyImage() -> UIImage {
if let url = URL(string: self.myUrl) {
self.myImage = self.downloadImage(url: url)
}
return self.myImage
}
func getDataFromUrl(url: URL, completion: #escaping (Data?, URLResponse?, Error?) -> ()) {
URLSession.shared.dataTask(with: url) { data, response, error in
completion(data, response, error)
}.resume()
}
func downloadImage(url: URL) {
print("Download Started")
getDataFromUrl(url: url) { data, response, error in
guard let data = data, error == nil else { return }
print(response?.suggestedFilename ?? url.lastPathComponent)
print("Download Finished")
DispatchQueue.main.async() {
self.myImage = UIImage(data: data)!
}
}
}
}
//in ViewController
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
DispatchQueue.main.async() {
self.theImageView.image = self.myClass?.getImage()
}
}
You have to set up the imageView's image once the asynchronous call back is completed.
class MyClass: NSObject {
// async function
func getMyImage(completion: #escaping (UIImage?) -> Void) {
// if the url is not available, completion with null
guard let url = URL(string: self.myUrl) else {
completion(nil)
return
}
getDataFromUrl(url: url) { data, response, error in
// if something goes wrong, completion with null
guard let data = data, error == nil else {
completion(nil)
return
}
print(response?.suggestedFilename ?? url.lastPathComponent)
print("Download Finished")
completion(UIImage(data: data)!)
}
}
}
// in ViewController
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
getImage { image in
// async function will get called when image is ready
DispatchQueue.main.async() { // set up your view in main thread
self.theImageView.image = image
}
}
}
I am making url calls thru an API that I created using swift as follows:
class API {
let apiEndPoint = "endpoint"
let apiUrl:String!
let consumerKey:String!
let consumerSecret:String!
var returnData = [:]
init(){
self.apiUrl = "https://myurl.com/"
self.consumerKey = "my consumer key"
self.consumerSecret = "my consumer secret"
}
func getOrders() -> NSDictionary{
return makeCall("orders")
}
func makeCall(section:String) -> NSDictionary{
let params = ["consumer_key":"key", "consumer_secret":"secret"]
Alamofire.request(.GET, "\(self.apiUrl)/\(self.apiEndPoint + section)", parameters: params)
.authenticate(user: self.consumerKey, password: self.consumerSecret)
.responseJSON { (request, response, data, error) -> Void in
println("error \(request)")
self.returnData = data! as NSDictionary
}
return self.returnData
}
}
I call this API in my UITableViewController to populate the table with SwiftyJSON library. However my returnData from the API is always empty. There is no problem with Alomofire calls as I can successfully retrieve value. My problem is how I am supposed to carry this data over to my table view controller?
var api = API()
api.getOrders()
println(api.returnData) // returnData is empty
As mattt points out, Alamofire is returning data asynchronously via a “completion handler” pattern, so you must do the same. You cannot just return the value immediately, but you instead want to change your method to not return anything, but instead use a completion handler closure pattern.
Nowadays, that might look like:
func getOrders(completionHandler: #escaping (Result<[String: Any]>) -> Void) {
performRequest("orders", completion: completionHandler)
}
func performRequest(_ section: String, completion: #escaping (Result<[String: Any]>) -> Void) {
let url = baseURL.appendingPathComponent(section)
let params = ["consumer_key": "key", "consumer_secret": "secret"]
Alamofire.request(url, parameters: params)
.authenticate(user: consumerKey, password: consumerSecret)
.responseJSON { response in
switch response.result {
case .success(let value as [String: Any]):
completion(.success(value))
case .failure(let error):
completion(.failure(error))
default:
fatalError("received non-dictionary JSON response")
}
}
}
Then, when you want to call it, you use this completion closure parameter (in trailing closure, if you want):
api.getOrders { result in
switch result {
case .failure(let error):
print(error)
case .success(let value):
// use `value` here
}
}
// but don't try to use the `error` or `value`, as the above closure
// has not yet been called
//
From the Alamofire README (emphasis added):
Networking in Alamofire is done asynchronously. Asynchronous programming may be a source of frustration to programmers unfamiliar with the concept, but there are very good reasons for doing it this way.
Rather than blocking execution to wait for a response from the server, a callback is specified to handle the response once it's received. The result of a request is only available inside the scope of a response handler. Any execution contingent on the response or data received from the server must be done within a handler.
Following is the complete flow for performing the 'Login Action' using Alamofire and Swift.
Alamofire v3.3
Swift 2.2
Xcode 7.3
I have used GCD and MBProgressHUD for my own convenience. Refactor and use as you like :)
func loginBtnTapped(sender: AnyObject) {
MBProgressHUD.showHUDAddedTo(self.view, animated: true)
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
let loginInfo : Dictionary<String,AnyObject> = ["email":"abc#g.com","password":"abc123"]
self.loginUser(loginInfo) { responseObject, error in
print("\(responseObject) \n \(error) ")
// Parsing JSON Below
let status = Int(responseObject?.objectForKey("status") as! String)
if status == 1 {
// Login Successfull...Move To New VC
}
else {
print(responseObject?.objectForKey("message"))! as! String)
}
return
}
dispatch_async(dispatch_get_main_queue()) {
MBProgressHUD.hideHUDForView(self.view, animated: true)
}
}
}
func loginUser(parameters:NSDictionary, completionHandler: (NSDictionary?, NSError?) -> ()) {
self.postRequest("http://qa.company.com/project/index.php/user/login",
paramDict: parameters as? Dictionary<String, AnyObject>,
completionHandler: completionHandler)
}
func postRequest(urlString: String, paramDict:Dictionary<String, AnyObject>? = nil,
completionHandler: (NSDictionary?, NSError?) -> ()) {
Alamofire.request(.POST, urlString, parameters: paramDict)
.responseJSON { response in
switch response.result {
case .Success(let JSON):
completionHandler(JSON as? NSDictionary, nil)
case .Failure(let error):
completionHandler(nil, error)
}
}
}
Details
xCode 9.1, Swift 4
Features:
Easy readable code
Ready templates (it's easy to add more requests)
Embedded solution with asynchronous data processing
Full examples
Sample 1
Return data using closure
Data1.searchRequest(term: "jack johnson") { json, error in
print(error ?? "nil")
print(json ?? "nil")
print("Update views")
}
Full sample 1
Data class
import Alamofire
class Data1 {
static fileprivate let queue = DispatchQueue(label: "requests.queue", qos: .utility)
static fileprivate let mainQueue = DispatchQueue.main
fileprivate class func make(request: DataRequest, closure: #escaping (_ json: [String: Any]?, _ error: Error?)->()) {
request.responseJSON(queue: Data1.queue) { response in
// print(response.request ?? "nil") // original URL request
// print(response.response ?? "nil") // HTTP URL response
// print(response.data ?? "nil") // server data
//print(response.result ?? "nil") // result of response serialization
switch response.result {
case .failure(let error):
Data1.mainQueue.async {
closure(nil, error)
}
case .success(let data):
Data1.mainQueue.async {
closure((data as? [String: Any]) ?? [:], nil)
}
}
}
}
class func searchRequest(term: String, closure: #escaping (_ json: [String: Any]?, _ error: Error?)->()) {
let request = Alamofire.request("https://itunes.apple.com/search?term=\(term.replacingOccurrences(of: " ", with: "+"))")
Data1.make(request: request) { json, error in
closure(json, error)
}
}
}
UIViewController
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
Data1.searchRequest(term: "jack johnson") { json, error in
print(error ?? "nil")
print(json ?? "nil")
print("Update views")
}
}
}
Sample 2
Return data using delegate
// ....
var data = Data2()
data.delegate = self
data.searchRequest(term: "jack johnson")
// ....
extension ViewController: Data2Delegate {
func searchRequest(response json: [String : Any]?, error: Error?) {
print(error ?? "nil")
print(json ?? "nil")
print("Update views")
}
}
Full sample 2
Data class
import Alamofire
protocol Data2Delegate: class {
func searchRequest(response json: [String: Any]?, error: Error?)
}
class Data2 {
fileprivate let queue = DispatchQueue(label: "requests.queue", qos: .utility)
fileprivate let mainQueue = DispatchQueue.main
weak var delegate: Data2Delegate?
fileprivate func make(request: DataRequest, closure: #escaping (_ json: [String: Any]?, _ error: Error?)->()) {
request.responseJSON(queue: queue) { response in
// print(response.request ?? "nil") // original URL request
// print(response.response ?? "nil") // HTTP URL response
// print(response.data ?? "nil") // server data
//print(response.result ?? "nil") // result of response serialization
switch response.result {
case .failure(let error):
self.mainQueue.async {
closure(nil, error)
}
case .success(let data):
self.mainQueue.async {
closure((data as? [String: Any]) ?? [:], nil)
}
}
}
}
func searchRequest(term: String) {
let request = Alamofire.request("https://itunes.apple.com/search?term=\(term.replacingOccurrences(of: " ", with: "+"))")
make(request: request) { json, error in
self.delegate?.searchRequest(response: json, error: error)
}
}
}
UIViewController
import UIKit
class ViewController: UIViewController {
private var data = Data2()
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
data.delegate = self
data.searchRequest(term: "jack johnson")
}
}
extension ViewController: Data2Delegate {
func searchRequest(response json: [String : Any]?, error: Error?) {
print(error ?? "nil")
print(json ?? "nil")
print("Update views")
}
}
Sample 3
Return data using PromiseKit
_ = data.searchRequest(term: "jack johnson").then { response in
print(response.error ?? "nil")
print(response.json ?? "nil")
print("Update views")
return .void
}
Full sample 3
Data class
import Alamofire
import PromiseKit
class Data3 {
fileprivate let queue = DispatchQueue(label: "requests.queue", qos: .utility)
fileprivate let mainQueue = DispatchQueue.main
fileprivate func make(request: DataRequest) -> Promise<(json:[String: Any]?, error: Error?)> {
return Promise { fulfill, reject in
request.responseJSON(queue: queue) { response in
// print(response.request ?? "nil") // original URL request
// print(response.response ?? "nil") // HTTP URL response
// print(response.data ?? "nil") // server data
//print(response.result ?? "nil") // result of response serialization
switch response.result {
case .failure(let error):
self.mainQueue.async {
fulfill((nil, error))
}
case .success(let data):
self.mainQueue.async {
fulfill(((data as? [String: Any]) ?? [:], nil))
}
}
}
}
}
func searchRequest(term: String) -> Promise<(json:[String: Any]?, error: Error?)> {
let request = Alamofire.request("https://itunes.apple.com/search?term=\(term.replacingOccurrences(of: " ", with: "+"))")
return make(request: request)
}
}
extension AnyPromise {
class var void: AnyPromise {
return AnyPromise(Promise<Void>())
}
}
UIViewController
import UIKit
import PromiseKit
class ViewController: UIViewController {
private var data = Data3()
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
_ = data.searchRequest(term: "jack johnson").then { response in
print(response.error ?? "nil")
print(response.json ?? "nil")
print("Update views")
return .void
}
}
}
To parse a json using Swifty JSON, here is how i am doing it.
For #Jenita _Alice4Real
func uploadScans(parameters: [String: AnyObject], completionHandler: (AnyObject?, NSError?) -> ()) {
makePostCall(CommonFunctions().getSaveSKUDataUrl(), parameters: parameters,completionHandler: completionHandler)
}
func makePostCall(url: String, parameters: [String: AnyObject], completionHandler: (AnyObject?, NSError?) -> ()) {
Alamofire.request(.POST, url, parameters: parameters)
.responseJSON { response in
switch response.result {
case .Success(let value):
completionHandler(value, nil)
case .Failure(let error):
completionHandler(nil, error)
}
}
}
uploadScans(params) { responseObject, error in
let json = JSON(responseObject!)
}