I created two views and then connect one to the other by ctrl-dragging and creating a segue. Gave this segue the identifier "functionOutput1"
I then created a function and programmatically triggered the segue created above based on certain output in a function.
performSegue(withIdentifier: "functionOuput1", sender: self)
The view segues okay but the contents of the view don't appear until a minute later.
Is there something else I need to be doing here?
EDIT:
I'm performing this segue in a callback function for a URLRequest
let task = session.dataTask(with: request as URLRequest, completionHandler: {
data, response, error -> Void in
if (error != nil) {
// there is an error with the request
print("error: ", error)
} else {
// Request was successful. Check the contents of the response.
print("response: ", response)
let httpResponse = response as! HTTPURLResponse
if httpResponse.statusCode != 200 {
print("problems with server request")
} else {
print("request successful")
//go to next page
performSegue(withIdentifier: "functionOuput1", sender: self)
}
}
})
This could be a threading issue. Because the data is returned asynchronously. You need to run the view updates on the main thread. You can do this with Swift 3.0 with the following code:
DispatchQueue.main.async {
// Your view updates here
}
Related
I need to fetch large amounts of data from an endpoint in an async way. The API endpoint serves a predefined amount of data at a time. After the first request I must check to see if I get a "next" url from the response and visit that link in order to continue the download. This recursive behaviour continues until all available data has been served, in other words paging functionality (HAL links). At this point I have implemented a func that download recursively, however: problem is that the final completion handler does not seem to get called.
Demo code: The ThingsApi is a class that encapsulates the actual API call. The important thing is that this class has an initial url and during recursion will get specific url's to visit asynchronously. I call the downloadThings() func and need to get notified when it is finished. It works if I leave recursion out of the equation. But when recursion is in play then nothing!
I have created a simplified version of the code that illustrate the logic and can be pasted directly into the Playground. The currentPage and pages var's are just there to demo the flow. The last print() statement does not get called. Leave the currentPage += 1 to experience the problem and set currentPage += 6 to avoid recursion. Clearly I am missing out of some fundamental concept here. Anyone?
import UIKit
let pages = 5
var currentPage = 0
class ThingsApi {
var url: URL?
var next: URL?
init(from url: URL) {
self.url = url
}
init() {
self.url = URL(string: "https://whatever.org")
}
func get(completion: #escaping (Data?, HTTPURLResponse?, Error?) -> Void) {
// *** Greatly simplified
// Essentially: use URLSession.shared.dataTask and download data async.
// When done, call the completion handler.
// Simulate that the download will take 1 second.
sleep(1)
completion(nil, nil, nil)
}
}
func downloadThings(url: URL? = nil, completion: #escaping (Bool, Error?, String?) -> Void) {
var thingsApi: ThingsApi
if let url = url {
// The ThingsApi will use the next url (retrieved from previous call).
thingsApi = ThingsApi(from: url)
} else {
// The ThingsApi will use the default url.
thingsApi = ThingsApi()
}
thingsApi.get(completion: { (data, response, error) in
if let error = error {
completion(false, error, "We have nothing")
} else {
// *** Greatly simplified
// Parse the data and save to db.
// Simulate that the thingsApi.next will have a value 5 times.
currentPage += 1
if currentPage <= pages {
thingsApi.next = URL(string: "https://whatever.org?page=\(currentPage)")
}
if let next = thingsApi.next {
// Continue downloading things recursivly.
downloadThings(url: next) { (success, error, feedback) in
guard success else {
completion(false, error, "failed")
return
}
}
} else {
print("We are done")
completion(true, nil, "done")
print("I am sure of it")
}
}
})
}
downloadThings { (success, error, feedback) in
guard success else {
print("downloadThings() failed")
return
}
// THIS DOES NOT GET EXECUTED!
print("All your things have been downloaded")
}
It seems like this is simply a case of "you forgot to call it yourself" :)
In this if statement right here:
if let next = thingsApi.next {
// Continue downloading things recursivly.
downloadThings(url: next) { (success, error, feedback) in
guard success else {
completion(false, error, "failed")
return
}
}
} else {
print("We are done")
completion(true, nil, "done")
print("I am sure of it")
}
Think about what happens on the outermost call to downloadThings, and execution goes into the if branch, and the download is successful. completion is never called!
You should call completion after the guard statement!
I have a login view controller that user Almofire library to get the response. I do the unit test on that controller but the test always fail. I think because take time to response.
My test case:
override func setUp() {
super.setUp()
continueAfterFailure = false
let vc = UIStoryboard(name: "Main", bundle: nil)
controllerUnderTest = vc.instantiateViewController(withIdentifier: "LoginVC") as! LoginViewController
controllerUnderTest.loadView()
}
override func tearDown() {
// Put teardown code here. This method is called after the invocation of each test method in the class.
controllerUnderTest = nil
super.tearDown()
}
func testLoginWithValidUserInfo() {
controllerUnderTest.email?.text = "raghad"
controllerUnderTest.pass?.text = "1234"
controllerUnderTest.loginButton?.sendActions(for: .touchUpInside)
XCTAssertEqual(controllerUnderTest.lblValidationMessage?.text , "logged in successfully")
}
I try to use:
waitForExpectations(timeout: 60, handler: nil)
But I got this error:
caught "NSInternalInconsistencyException"
almofire function in login presenter :
func sendRequest(withParameters parameters: [String : String]) {
Alamofire.request(LOGINURL, method: .post, parameters: parameters).validate ().responseJSON { response in
debugPrint("new line : \(response)" )
switch response.result {
case .success(let value):
let userJSON = JSON(value)
self.readResponse(data: userJSON)
case .failure(let error):
print("Error \(String(describing: error))")
self.delegate.showMessage("* Connection issue ")
}
self.delegate.removeLoadingScreen()
//firebase log in
Auth.auth().signIn(withEmail: parameters["email"]!, password: parameters["pass"]!) { [weak self] user, error in
//guard let strongSelf = self else { return }
if(user != nil){
print("login with firebase")
}
else{
print("eroor in somthing")
}
if(error != nil){
print("idon now")
}
// ...
}
}
}
func readResponse(data: JSON) {
switch data["error"].stringValue {
case "true":
self.delegate.showMessage("* Invalid user name or password")
case "false":
if data["state"].stringValue=="0" {
self.delegate.showMessage("logged in successfully")
}else {
self.delegate.showMessage("* Inactive account")
}
default:
self.delegate.showMessage("* Connection issue")
}
}
How can I solve this problem? :(
Hi #Raghad ak, welcome to Stack Overflow 👋.
Your guess about the passage of time preventing the test to succeed is correct.
Networking code is asynchronous. After the test calls .sendActions(for: .touchUpInside) on your login button it moves to the next line, without giving the callback a chance to run.
Like #ajeferson's answer suggests, in the long run I'd recommend placing your Alamofire calls behind a service class or just a protocol, so that you can replace them with a double in the tests.
Unless you are writing integration tests in which you'd be testing the behaviour of your system in the real world, hitting the network can do you more harm than good. This post goes more into details about why that's the case.
Having said all that, here's a quick way to get your test to pass. Basically, you need to find a way to have the test wait for your asynchronous code to complete, and you can do it with a refined asynchronous expectation.
In your test you can do this:
expectation(
for: NSPredicate(
block: { input, _ -> Bool in
guard let label = input as? UILabel else { return false }
return label.text == "logged in successfully"
}
),
evaluatedWith: controllerUnderTest.lblValidationMessage,
handler: .none
)
controllerUnderTest.loginButton?.sendActions(for: .touchUpInside)
waitForExpectations(timeout: 10, handler: nil)
That expectation will run the NSPredicate on a loop, and fulfill only when the predicate returns true.
You have to somehow signal to your tests that are safe to proceed (i.e. expectation is fulfilled). The ideal approach would be decouple that Alamofire code and mock its behavior when testing. But just to answer your question, you might want to do the following.
In your view controller:
func sendRequest(withParameters parameters: [String : String], completionHandler: (() -> Void)?) {
...
Alamofire.request(LOGINURL, method: .post, parameters: parameters).validate ().responseJSON { response in
...
// Put this wherever appropriate inside the responseJSON closure
completionHandler?()
}
}
Then in your tests:
func testLoginWithValidUserInfo() {
controllerUnderTest.email?.text = "raghad"
controllerUnderTest.pass?.text = "1234"
controllerUnderTest.loginButton?.sendActions(for: .touchUpInside)
let expectation = self.expectation(description: "logged in successfully)
waitForExpectations(timeout: 60, handler: nil)
controllerUnderTest.sendRequest(withParameters: [:]) {
expectation.fulfill()
}
XCTAssertEqual(controllerUnderTest.lblValidationMessage?.text , "logged in successfully")
}
I know you have some intermediate functions between the button click and calling the sendRequest function, but this is just for you to get the idea. Hope it helps!
I customize refreshTokens functions according to Alamofire guide.
I'd like to reroute to Login View when refreshTokens failed and got 401 status from API server (for other error status like 400 or 500, just display error message in the view).
Currently I use UserDefaults to notice 401 status to the view (, who call the Alamofire request).
I'd like to know if there's better approach to notice "refreshToken status" to the view (or approach to share the status variable with view and oauth2handler).
thanks!
OAuth2Handler
manager.request(urlString, method: .post, parameters: parameters, encoding: URLEncoding.default)
.responseJSON { [weak self] response in
guard let strongSelf = self else { return }
if
let json = response.result.value as? [String: Any],
let accessToken = json["access_token"] as? String
{
completion(true, accessToken)
} else {
if let status = response.response?.statusCode, status == 401 {
UserDefaults.standard.set(true, forKey: "login_required")
}
completion(false, nil)
}
strongSelf.isRefreshing = false
}
ViewController action when some button clicked
_ = client.request(API.addLike(json: comment))
.subscribe(
onSuccess: { (response) in
// successful!
},
onError: { (err) in
let loginRequired = UserDefaults.standard.bool(forKey: "login_required")
if loginRequired == true {
print("refresh token is wrong or expired. login required")
// transition to LoginView
} else {
print("request is invalid or server is down.")
}
}
)
I have recently managed the same situation for one of my app. I have created an OAuthManager class which inherits from RequestAdapter and RequestRetrier.
In the func adapt(_ urlRequest: URLRequest) throws -> URLRequest, I adapt my request with my Authorization token.
In func should(_ manager: SessionManager, retry request: Request, with error: Error, completion: #escaping RequestRetryCompletion) I am checking the result of the request before sending to the completion handler of Alamofire.
In my case, I can receive 401 error code for expired access tokens or simply because the user is not authorized to perform this action. So, I am checking the server message sent by my REST API in order to be sure that the access token is expired and request a new one.
If the refresh token API returns an error, I display the LoginViewController directly from the should function by doing:
let rootViewController = UIStoryboard(name: "Main", bundle: Bundle.main).instantiateViewController(withIdentifier: "WELCOME_NAVIGATION")
UIApplication.shared.keyWindow?.rootViewController = rootViewController
I can do this because my login methods are available from an UIViewController. If you want to use an UIView, you can maybe add a subview to UIApplication.shared.keyWindow?.rootViewController.view.
If you want to display a notification or something like this, maybe it will be better to use NotificationCenter to trigger some code in your UIView.
Regards,
IMACODE
I would like to only execute a segue if I get a certain response from the server. In swift, how can I wait until I get a response to continue?
Bottom line, you don't "wait" for the response, but rather simply specify what you want to happen when the response comes in. For example, if you want to perform a segue when some network request is done, you should employ the completion handler pattern.
The issue here is that you're probably accustomed to just hooking your UI control to a segue in Interface Builder. In our case, we don't want to do that, but rather we want to perform the network request, and then have its completion handler invoke the segue programmatically. So, we have to create a segue that can be performed programmatically and then hook your button up to an #IBAction that performs the network request and, if appropriate, performs the segue programmatically. But, note, there should be no segue hooked up to the button directly. We'll do that programmatically.
For example:
Define the segue to be between the two view controllers by control-dragging from the view controller icon in the bar above the first scene to the second scene:
Give that segue a storyboard identifier by selecting the segue and going to the "Attributes Inspector" tab:
Hook up the button (or whatever is going to trigger this segue) to an #IBAction.
Write an #IBAction that performs network request and, upon completion, programmatically invokes that segue:
#IBAction func didTapButton(_ sender: Any) {
let request = URLRequest(...). // prepare request however your app requires
let waitingView = showWaitingView() // present something so that the user knows some network request is in progress
// perform network request
let task = URLSession.shared.dataTask(with: request) { data, response, error in
// regardless of how we exit this, now that request is done, let's
// make sure to remove visual indication that network request was underway
defer {
DispatchQueue.main.async {
waitingView.removeFromSuperview()
}
}
// make sure there wasn't an error; you'll undoubtedly have additional
// criteria to apply here, but this is a start
guard let data = data, error == nil else {
print(error ?? "Unknown error")
return
}
// parse and process the response however is appropriate in your case, e.g., if JSON:
//
// guard let responseObject = try? JSONSerialization.jsonObject(with data) else {
// // handle parsing error here
// return
// }
//
// // do whatever you want with the parsed JSON here
// do something with response
DispatchQueue.main.async {
performSegue(withIdentifier: "SegueToSceneTwo", sender: self)
}
}
task.resume()
}
/// Show some view so user knows network request is underway
///
/// You can do whatever you want here, but I'll blur the view and add `UIActivityIndicatorView`.
private func showWaitingView() -> UIView {
let effectView = UIVisualEffectView(effect: UIBlurEffect(style: .Dark))
effectView.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(effectView)
NSLayoutConstraint.activateConstraints([
effectView.leadingAnchor.constraintEqualToAnchor(view.leadingAnchor),
effectView.trailingAnchor.constraintEqualToAnchor(view.trailingAnchor),
effectView.topAnchor.constraintEqualToAnchor(view.topAnchor),
effectView.bottomAnchor.constraintEqualToAnchor(view.bottomAnchor)
])
let spinner = UIActivityIndicatorView(activityIndicatorStyle: .WhiteLarge)
effectView.addSubview(spinner)
spinner.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activateConstraints([
spinner.centerXAnchor.constraintEqualToAnchor(view.centerXAnchor),
spinner.centerYAnchor.constraintEqualToAnchor(view.centerYAnchor)
])
spinner.startAnimating()
return effectView
}
My problem is when I try to go another view after some api call finishes, it wont go to the next view. Here is the code below. Thanks in advance.
var task = NSURLSession.sharedSession().dataTaskWithURL(url!, completionHandler: {
(data, response, error) in //println(response)
//println(error)
self.myWeather.apiCallData = JSON(data: data)
self.myWeather.apiCallError = error
println("api call finished")
if error == nil {
println("no error")
let weatherView = self.storyboard?.instantiateViewControllerWithIdentifier("WeatherView") as WeatherViewController
weatherView.myWeather = self.myWeather
self.navigationController?.pushViewController(weatherView, animated: false)
}
}).resume()
It does print api call finished and no error on console. But it doesn't go to the other scene.
The problem is that the completion handler code of the dataTaskWithURL method runs in a background secondary thread, not in the main thread (where view controller transition can happen).
Wrap the call to pushViewController in a main thread queue closure:
...
dispatch_async(dispatch_get_main_queue(), {
let navigationVC = self.navigationController
navigationVC?.pushViewController(weatherView, animated: false)
})
...
I have written the code in two lines to avoid a swift compiler bug (single statement and closure return value: see this). You can also write it as:
...
dispatch_async(dispatch_get_main_queue(), {
(self.navigationController)?.pushViewController(weatherView, animated: false)
return
})
...