I am writing the iOS application using swift 4.2. I am making a service call to logout user.
I need to know where to use main thread (DispatchQueue.main.async).
Here is my code:
private func handleLogoutCellTap() {
logoutUseCase?.logout() { [weak self] (result) in
guard let self = self else { return }
switch result {
case let (.success(didLogout)):
didLogout ? self.handleSuccessfullLogout() : self.handleLogoutError(with: nil)
case let (.failure(error)):
self.handleLogoutError(with: error)
}
}
}
logoutUseCase?.logout() makes a service call and returns #escaping completion. Should I use DispatchQueue.main.async on this whole handleLogoutCellTap() function or just in a handling segment?
Move the control to main thread wherever you're updating the UI after receiving the response of logout.
If handleSuccessfullLogout() and handleLogoutError(with:) methods perform any UI operation, you can embed the whole switch statement in DispatchQueue.main.async, i,e.
private func handleLogoutCellTap() {
logoutUseCase?.logout() { [weak self] (result) in
guard let self = self else { return }
DispatchQueue.main.async { //here.....
switch result {
//rest of the code....
}
}
}
}
Related
I'm downloading some JSON from an API, but there is another prerequisite (an animation) that must be complete before we move to the next screen.
I've decided to use DispatchGroup to do this, but also need to have a reload as well.
I've come up with a solution that uses a completion handler that is either dispatchGroup.leave or simply moving to the next screen, since we only need to download the data once.
let dispatchGroup = DispatchGroup()
var userName: String?
func fetchData() {
dispatchGroup.enter()
dispatchGroup.enter()
resolveDataRequirements(dispatchGroup.leave)
dispatchGroup.notify(queue: .main) { [weak self] in
self?.moveToNextScreen()
}
}
func resolveDataRequirements(_ completion: #escaping(() -> Void)) {
api.resolve { [weak self] result in
switch result {
case .success(let user):
self?.userName = user
completion()
case .failure:
break
}
}
}
func moveToNextScreen() {
// move to next screen, but passes the user
}
// reload data, and once the data is downloaded move to next screen
func reloadData() {
resolveDataRequirements(moveToNextScreen)
}
// the user might choose to fetch data
fetchData()
// now if the user wanted to reload
reloadData()
Now the problem is that this is in a view model - so the user String is effectively a state that I wish to eradicate.
Is there any way I can pass the user String to dispatchGroup.notify or similar?
You can use inout properties and change userName scope like this:
func fetchData() {
var userName = ""
dispatchGroup.enter()
dispatchGroup.enter()
resolveDataRequirements(dispatchGroup.leave, &userName)
dispatchGroup.notify(queue: .main) { [weak self] in
self?.moveToNextScreen(userName)
}
}
func resolveDataRequirements(_ completion: #escaping(() -> Void), _ userName: inout String) {
api.resolve { [weak self] result in
switch result {
case .success(let user):
userName = user
completion()
case .failure:
break
}
}
}
func moveToNextScreen(_ userName: String) {
print(userName)
}
I just don't understand why you are calling enter() twice and leave() just once
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'm using DispatchGroup.enter() and leave() to process a helper class's reverseG async function. Problem is clear, I'm using mainViewController's object to call mainViewControllers's dispatchGroup.leave() in helper class! Is there a way to do it?
Same code works when reverseG is declared in the main view controller.
class Geo {
var obj = ViewController()
static func reverseG(_ coordinates: CLLocation, _ completion: #escaping (CLPlacemark) -> ()) {
let geoCoder = CLGeocoder()
geoCoder.reverseGeocodeLocation(coordinates) { (placemarks, error) in
if let error = error {
print("error: \(error.localizedDescription)")
}
if let placemarks = placemarks, placemarks.count > 0 {
let placemark = placemarks.first!
completion(placemark) // set ViewController's properties
} else {
print("no data")
}
obj.dispatchGroup.leave() // ** ERROR **
}
}
}
Function call from main view controller
dispatchGroup.enter()
Geo.reverseG(coordinates, setValues) // completionHandler: setValues
dispatchGroup.notify(queue: DispatchQueue.main) {
// call another function on completion
}
Every leave call must have an associated enter call. If you call leave without having first called enter, it will crash. The issue here is that you're calling enter on some group, but reverseG is calling leave on some other instance of ViewController. I'd suggest passing the DispatchGroup as a parameter to your reverseG method. Or, better, reverseG shouldn't leave the group, but rather put the leave call inside the completion handler that reserveG calls.
dispatchGroup.enter()
Geo.reverseG(coordinates) { placemark in
defer { dispatchGroup.leave() }
guard let placemark = placemark else { return }
// use placemark here, e.g. call `setValues` or whatever
}
dispatchGroup.notify(queue: DispatchQueue.main) {
// call another function on completion
}
And
class Geo {
// var obj = ViewController()
static func reverseG(_ coordinates: CLLocation, completion: #escaping (CLPlacemark?) -> Void) {
let geoCoder = CLGeocoder()
geoCoder.reverseGeocodeLocation(coordinates) { placemarks, error in
if let error = error {
print("error: \(error.localizedDescription)")
}
completion(placemarks?.first)
// obj.dispatchGroup.leave() // ** ERROR **
}
}
}
This keeps the DispatchGroup logic at one level of the app, keeping your classes less tightly coupled (e.g. the Geo coder doesn't need to know whether the view controller uses dispatch groups or not).
Frankly, I'm not clear why you're using dispatch group at all if there's only one call. Usually you'd put whatever you call inside the completion handler, simplifying the code further. You generally only use groups if you're doing a whole series of calls. (Perhaps you've just simplified your code snippet whereas you're really doing multiple calls. In that case, a dispatch group might make sense. But then again, you shouldn't be doing concurrent geocode requests, suggesting a completely different pattern, altogether.
Passed dispatchGroup as parameter with function call and it worked.
Geo.reverseG(coordinates, dispatchGroup, setValues)
my two cents to show how can work:
(maybe useful for others..)
// Created by ing.conti on 02/02/21.
//
import Foundation
print("Hello, World!")
let r = AsyncRunner()
r.runMultiple(args: ["Sam", "Sarah", "Tom"])
class AsyncRunner{
static let shared = AsyncRunner()
let dispatchQueue = DispatchQueue(label: "MyQueue", qos:.userInitiated)
let dispatchGroup = DispatchGroup.init()
func runMultiple(args: [String]){
let count = args.count
for i in 0..<count {
dispatchQueue.async(group: dispatchGroup) { [unowned self] in
dispatchGroup.enter()
self.fakeTask(arg: args[i])
}
}
_ = dispatchGroup.wait(timeout: DispatchTime.distantFuture)
}
func fakeTask(arg: String){
for i in 0..<3 {
print(arg, i)
sleep(1)
}
dispatchGroup.leave()
}
}
When I need to read data from HealthKit this is how my code looks like:
let stepsCount = HKQuantityType.quantityTypeForIdentifier(HKQuantityTypeIdentifierStepCount)
let stepsSampleQuery = HKSampleQuery(sampleType: stepsCount,
predicate: nil,
limit: 100,
sortDescriptors: nil)
{ [unowned self] (query, results, error) in
if let results = results as? [HKQuantitySample] {
self.steps = results
// Update some UI
}
self.activityIndicator.stopAnimating()
}
healthStore?.executeQuery(stepsSampleQuery)
This specific code was extracted from here for demo purpose.
So my question is:
How can I unit test this kind of code ?
I encapsulate this code in a function in a model class that knows nothing about the UI. It works like this:
At the place the you have your
// Update some UI
call a completion closure, that was passed to the function using a parameter.
You call this function from your controller class like this
hkModel.selectSteps() {
[unowned self] (query, results, error) in
// update UI
}
This way you have a clean separation between your query logic in the model class and your UIController code.
Now you can easily write a unit test calling the same method:
func testSteps() {
hkModel.selectSteps() {
[unowned self] (query, results, error) in
// XCTAssert(...)
}
}
The last thing you need is to respect that your test code is called asynchronously:
let stepExpectationEnd = expectationWithDescription("step Query")
hkModel.selectSteps() {
[unowned self] (query, results, error) in
// XCTAssert(...)
stepExpectationEnd.fulfill()
}
waitForExpectationsWithTimeout(10.0) {
(error: NSError?) in
if let error = error {
XCTFail(error.localizedDescription)
}
}
update
Because you asked:
I handle authorization at the test setup. looks like this:
var healthData: HealthDataManager?
override func setUp() {
super.setUp()
healthData = HealthDataManager()
XCTAssert(healthData != nil, "healthDadta must be there")
let authorizationAndAScheduleExpectation = expectationWithDescription("Wait for authorizatiion. Might be manual the first time")
healthData?.authorizeHealthKit({ (success: Bool, error: NSError?) -> Void in
print ("success: \(success) error \(error?.localizedDescription)")
// fails on iPad
XCTAssert(success, "authorization error \(error?.localizedDescription)")
self.healthData?.scheduleAll() {
(success:Bool, error:ErrorType?) -> Void in
XCTAssert(success, "scheduleAll error \(error)")
authorizationAndAScheduleExpectation.fulfill()
}
})
waitForExpectationsWithTimeout(60.0) {
error in
if let error = error {
XCTFail(error.localizedDescription)
}
}
}
The first time you run this code in a simulator, you have to approve authorization manually.
After the first run the tests run without manual intervention.