I have an observable that emits a list of CNContacts, and I want to reload the list when there is a change to the Contacts database (.CNContactStoreDidChange).
So the observable should emit a value on subscription, and whenever the other observable (the notification) emits a value. That sounds like combining them with withLatestFrom, but it doesn't emit anything.
let myContactKeys = [
CNContactIdentifierKey as CNKeyDescriptor,
CNContactFormatter.descriptorForRequiredKeys(for: .fullName)
]
func fetchContacts(by identifiers: [String],
contactKeys: [CNKeyDescriptor]) -> Observable<Event<[CNContact]>> {
return Observable<[String]>.just(identifiers)
.withLatestFrom(NotificationCenter.default.rx.notification(Notification.Name.CNContactStoreDidChange)) { ids, _ in ids}
.flatMap { ids in
Observable<[CNContact]>.create { observer in
let predicate = CNContact.predicateForContacts(withIdentifiers: ids)
do {
let contacts = try CNContactStore().unifiedContacts(matching: predicate, keysToFetch: contactKeys)
observer.onNext(contacts)
} catch {
observer.onError(error)
}
return Disposables.create()
}
.materialize()
}
.observeOn(MainScheduler.instance)
.share(replay: 1)
.debug()
}
fetchContacts(by: ["123"], contactKeys: myContactKeys)
.subscribe(
onNext: { contacts in
contacts.forEach { print($0.fullName) }
},
onError: { error in
print(error.localizedDescription)
})
.dispose(by: disposeBag)
The problem with your code is that you are starting with Observable<[String]>.just(identifiers) which will emit your identifiers and immediately complete. You don't want it to complete, you want it to continue to emit values whenever the notification comes in.
From your description, it sounds like you want something like the below. It emits whenever the notification fires, and starts with the contacts.
let myContactKeys = [
CNContactIdentifierKey as CNKeyDescriptor,
CNContactFormatter.descriptorForRequiredKeys(for: .fullName)
]
func fetchContacts(by identifiers: [String], contactKeys: [CNKeyDescriptor]) -> Observable<Event<[CNContact]>> {
func update() throws -> [CNContact] {
let predicate = CNContact.predicateForContacts(withIdentifiers: identifiers)
return try CNContactStore().unifiedContacts(matching: predicate, keysToFetch: contactKeys)
}
return Observable.deferred {
NotificationCenter.default.rx.notification(Notification.Name.CNContactStoreDidChange)
.map { _ in }
.map(update)
.materialize()
}
.startWith({ () -> Event<[CNContact]> in
do {
return Event.next(try update())
}
catch {
return Event.error(error)
}
}())
.share(replay: 1)
.debug()
}
Related
Given an array of urls, is there a way to run those at once simultaneously? But in such a way so as soon as there is one success move to the next request using that successful url.
So far I tried chaining concatMap, and failed with zip.
func updateAccountInfo() -> Single<Bool> {
var disposable: Disposable? = nil
return Single<Bool>.create { observer in
do {
var urls = try self.settings.domains.value()
disposable = Observable.from(urls)
.enumerated()
.concatMap { index, url -> Single<URL> in
return self.verifyUrl(url)
}
.concatMap { url -> Single<Account> in
return self.apiManager.loadAccountInfo(from: url)
}
.observeOn(MainScheduler.instance)
.do(onNext: { (account: AccountInfo) in
// use account unfo here
disposable!.dispose()
})
.subscribe()
} catch {
observer(.error(error))
}
return Disposables.create()
}
}
Tried like so too:
disposable = Observable.from(urls)
.enumerated()
.concatMap { index, url -> Single<(Bool, URL)> in
return self.verifyUrl(url)
}
.subscribe(onNext: { reachable, url in
if reachable {
self.apiManager.loadAccountInfo(from: url)
.subscribe(onSuccess: { accountInfo in
// use account info here
}, onError: { error in
})
.disposed(by: self.bag)
disposable!.dispose()
} else {
}
}, onError: { error in
}, onCompleted: {
})
Maybe I use zip but how would I create an array of verifyUrl(url) calls? Does zip accept arrays of Observable at all?
let obs = Observable.from(urls)
.enumerated()
.concatMap { index, url -> Single<URL> in
return self.verifyUrl(url)
}
let test = Observable
.zip(obs).map { [urls] in
return [urls]
}
If I understand the question correctly, you are looking for something like this:
func example() throws {
let urls = try self.settings.domains.value()
Observable.merge(urls.map { verifyUrl($0).asObservable() })
.flatMap { [apiManager] url in
apiManager!.loadAccountInfo(from: url)
}
.observe(on: MainScheduler.instance)
.subscribe(onNext: { account in
// use account unfo here
})
.disposed(by: self.disposeBag)
}
But it's hard to tell. Your code samples are a bit jumbled. Putting all your code in a Single.create is odd. Returning a Disposables.create() from the closure when you have a disposable to return is odd. Calling dispose() on a disposable inside the do block is odd. So much weirdness... I suggest you post some code on https://codereview.stackexchange.com or look at sample code.
I want to add a value to Firestore. When finished I want to return the added value. The value does get added to Firestore successfully. However, the value does not go through sink.
This is the function that does not work:
func createPremium(user id: String, isPremium: Bool) -> AnyPublisher<Bool,Never> {
let dic = ["premium":isPremium]
return Future<Bool,Never> { promise in
self.db.collection(self.dbName).document(id).setData(dic, merge: true) { error in
if let error = error {
print(error.localizedDescription)
} else {
/// does get called
promise(.success(isPremium))
}
}
}.eraseToAnyPublisher()
}
I made a test function that works:
func test() -> AnyPublisher<Bool,Never> {
return Future<Bool,Never> { promise in
promise(.success(true))
}.eraseToAnyPublisher()
}
premiumRepository.createPremium(user: userID ?? "1234", isPremium: true)
.sink { receivedValue in
/// does not get called
print(receivedValue)
}.cancel()
test()
.sink { recievedValue in
/// does get called
print("Test", recievedValue)
}.cancel()
Also I have a similar code snippet that works:
func loadExercises(category: Category) -> AnyPublisher<[Exercise], Error> {
let document = store.collection(category.rawValue)
return Future<[Exercise], Error> { promise in
document.getDocuments { documents, error in
if let error = error {
promise(.failure(error))
} else if let documents = documents {
var exercises = [Exercise]()
for document in documents.documents {
do {
let decoded = try FirestoreDecoder().decode(Exercise.self, from: document.data())
exercises.append(decoded)
} catch let error {
promise(.failure(error))
}
}
promise(.success(exercises))
}
}
}.eraseToAnyPublisher()
}
I tried to add a buffer but it did not lead to success.
Try to change/remove .cancel() method on your subscriptions. Seems you subscribe to the publisher, and then immediately cancel the subscription. The better option is to retain and store all your subscriptions in the cancellable set.
RxSwift one more question about error handling:
I'm using Alamofire+RxAlamofire this way:
SessionManager.default.rx.responseJSON(.post, url, parameters:params)
example:
func login() -> Observable<Int> {
let urlString = ...
let params = ...
return SessionManager.default.rx.responseJSON(.post, url, parameters:params)
.rxJsonDefaultResponse()
.map({ (data) in
data["clientId"] as! Int
})
}
....
extension ObservableType where Element == (HTTPURLResponse, Any) {
func rxJsonDefaultResponse() -> Observable<Dictionary<String, Any>> {
return self.asObservable().map { data -> Dictionary<String, Any> in
if... //error chechings
throw NSError(domain: ..,
code: ...,
userInfo: ...)
}
...
return json
}
}
}
using:
loginBtn.rx.tap
.flatMap{ _ in
provider.login()
}.subscribe(onNext: { id in
...
}, onError: { (er) in
ErrorPresentationHelper.showErrorAlert(for: er)
})
.disposed(by: bag)
So if error occurred everything works as intended: error alert shows and 'loginBtn.rx.tap' disposed, but I need it to be still alive, what's my strategy here if I want to use onError block?
You can use materialize function in rxSwift. It will convert any Observable into an Observable of its events. So that you will be listening to Observable<Event<Int>> than Observable<Int>. Any error thrown from the flatmap would be captured as error event in your subscription block's onNext and can be handled there. And your subscription would still be alive. Sample code would be as follows.
button.rx.tap.flatMap { _ in
return Observable.just(0)
.flatMap { _ -> Observable<Int> in
provider.login()
}.materialize()
}.subscribe(onNext: { event in
switch event {
case .next:
if let value = event.element {
print(value) //You will be getting your value here
}
case .error:
if let error = event.error {
print(error.localizedDescription) //You will be getting your captured error here
}
case .completed:
print("Subscription completed")
}
}) {
print("Subscription disposed")
}.disposed(by: disposeBag)
Hope it helps. You can checkout the materialize extension here.
So basically I have two actions I need to execute:
first is login
second is get user profile
They have to be done in right order because getting user profile cannot be done without logging in first.
So I had bunch of code that looked like this:
func signIn(signinParameters: SignInParameters) -> Observable<SignInResult> {
return Observable<SignInResult>.create { [unowned self] observer in
self.signinParameters = signinParameters
self.apiConnector
.signIn(with: signinParameters)
.do(onNext: { [weak self] signinResult in
self!.apiConnector
.get()
.do(onNext: { user in
let realm = RealmManager.shared.newRealm()!
let realmUser = RealmUser()
realmUser.configure(with: user, in: realm)
try? realm.write {
realm.add(realmUser, update: true)
}
self!.setState(.authenticated)
observer.onNext(signinResult)
}, onError: { (error) in
observer.onError(error)
}, onCompleted: {
observer.onCompleted()
}).subscribe()
}, onError: { error in
observer.onError(error)
}, onCompleted: {
print("completed")
observer.onCompleted()
}).subscribe()
return Disposables.create()
}
I know this is not right because I cannot send onNext signal with signin result when both actions are finished. I've been reading and I figured out i need to flatmap both actions, combine them into one signal and then manipulate signinresult but I dont have a clue how to do that. So any help would be nice.
Thank you
EDIT 1:
so I've refactored code to look something like this, but there is still problem that I can't send signal when BOTH actions are finished, or am I wrong?
func signIn(signinParameters: SignInParameters) -> Observable<SignInResult> {
return Observable<SignInResult>.create { [unowned self] observer in
self.signinParameters = signinParameters
self.apiConnector
.signIn(with: signinParameters)
.do(onNext: { (result) in
}, onError: { (error) in
}, onCompleted: {
})
.flatMap({ (result) -> Observable<User> in
self.apiConnector.get().asObservable()
})
.do(onNext: { (user) in
}, onError: { (error) in
}, onCompleted: {
}).subscribe()
return Disposables.create()
}
}
Your code is not very clean and it is hard to understand what is going on (my opinion).
If you need two actions to be executed you can create two functions:
struct Parameters{}
struct Profile{}
struct User{}
func login(parameters: Parameters) -> Observable<User> {
// get user
}
func profile(user: User) -> Observable<Profile> {
// get profile
}
func serial(parameters: Parameters) -> Observable<Profile> {
return login(parameters: parameters).flatMap({ profile(user: $0) })
}
login function or profile function can be also split into smaller functions if required:
func profileStored(user: User) -> Observable<Profile?> {
// get stored profile
}
func profileRequested(user: User) -> Observable<Profile> {
// get profile from network
}
func profile(user: User) -> Observable<Profile> {
let observable = profileStored(user: user)
.shareReplayLatestWhileConnected()
let observableStored = observable
.filter({ $0 != nil })
.map({ $0! })
.shareReplayLatestWhileConnected()
let observableRequested = observable
.filter({ $0 == nil })
.flatMap({ _ in profileRequested(user: user) })
.shareReplayLatestWhileConnected()
return Observable
.of(observableStored, observableRequested)
.merge()
.shareReplayLatestWhileConnected()
}
As a result you can mix smaller functions with flatMap or any other operator.
That is how I do it. Hope it'll be helpful
I have and observable that never sends onNext if its returned by a function, but if i subscribe to it in the function that returns it, onNext is called.
class InfoViewModel {
func refreshPushToken() {
PushNotificationService.sharedInstance.pushToken!
.flatMapLatest { (pushToken: String) -> Observable<Result<User>> in
return UserService.registerPushToken(pushToken)
}
.subscribe { (event ) in
print(event)
}
.addDisposableTo(disposeBag)
}
}
struct UserService {
....
static func registerPushToken(_ pushToken: String) -> Observable<Result<User>> {
...
return self.postUser(user: user)
}
static fileprivate func postUser(user: User) -> Observable<Result<User>> {
let rxProvider: RxMoyaProvider<Backend> = RxMoyaProvider<Backend>(endpointClosure: Backend.endpointClosure)
return rxProvider.request(Backend.register(user: user))
.mapObject(type: User.self)
.map({ (user: User) -> Result<User> in
LogService.log(level: .debug, action: "postUser", message: "Posted user with success", parameters: ["user": user.deviceId])
return .success(user)
})
.catchError({ error -> Observable<Result<User>> in
LogService.log(level: .error, action: "postUser", message: "Error posting user", parameters: ["user": user.deviceId, "error": error.localizedDescription])
return Observable.just(.failure(error))
})
}
}
But if I do this
rxProvider.request(Backend.register(user: user))
...
.subscribe { (event ) in
print(event)
}
in the UserService, i will get a next event.
I have tried to use debug() on the observable in InfoViewModel, there is a subscription, i just never receive any events.
So i figured it out, I was creating the RxMoyaProvider inside the method, so as soon as i went out of the scope of the method, it was deallocated. Which means that when was subscribing to it, it could no longer create the request. The reason that this wouldn't fail is because of how the observable is created
open func request(_ token: Target) -> Observable<Response> {
// Creates an observable that starts a request each time it's subscribed to.
return Observable.create { [weak self] observer in
let cancellableToken = self?.request(token) { result in
switch result {
case let .success(response):
observer.onNext(response)
observer.onCompleted()
case let .failure(error):
observer.onError(error)
}
}
return Disposables.create {
cancellableToken?.cancel()
}
}
}
As you can see, the request is called upon subscription, but since self had been deallocated the request was never fired. And all i got back was an empty observable.