I have this function:
func makeRepoRequest() -> Single<[String: Any]> {
return Single<[String: Any]>.create {[weak self] observer in
guard let something = self?.temp else {
let disposeBag = DisposeBag()
self?.getRepo("364").subscribe(onSuccess: { content in
observer(.success(content))
}, onError: { error in
observer(.error(error))
}).disposed(by: disposeBag)
return Disposables.create()
}
observer(.success(something))
return Disposables.create()
}
}
is subscribe to this function:
func getRepo(_ repo: String) -> Single<[String: Any]> {
return Single<[String: Any]>.create { single in
print(repo)
let url = "https://api.github.com/repositories?since=\(repo)"
print(url)
let task = URLSession.shared.dataTask(with: URL(string:url)!) { data, _, error in
if let error = error {
single(.error(error))
return
}
guard let data = data,
let json = try? JSONSerialization.jsonObject(with: data, options: []),
let result = json as? [String: Any] else {
let error = NSError(domain: "Decoding", code: 0, userInfo: nil)
single(.error(error))
return
}
single(.success(result))
}
task.resume()
return Disposables.create()
}
}
but for some reason the subscription it never gets a call back. Any of you knows why the subscription never gets a call back?
I'll really appreciate your help.
Your makeRepoRequest() is defined incorrectly. The disposable you create inside the closure should be the one that you return. There shouldn't be any disposeBag in there, also you need to unwrap self and make sure something is emitted if self doesn't exist, also if you are going to keep a cache in temp you really should assign to it...
func makeRepoRequest() -> Single<[String: Any]> {
return Single<[String: Any]>.create { [weak self] observer in
guard let this = self else {
observer(.error(MyError.missingSelf))
return Disposables.create()
}
guard !this.temp.isEmpty else {
return this.getRepo("364").subscribe(onSuccess: { content in
this.temp = content
observer(.success(content))
}, onError: { error in
observer(.error(error))
})
}
observer(.success(this.temp))
return Disposables.create()
}
}
However, since you are just emitting content with no changes, you don't even need to use .create(_:). So something like this:
func makeRepoRequest() -> Single<[String: Any]> {
if !temp.isEmpty {
return getRepo("364")
.do(onSuccess: { [weak self] in self?.temp = $0 })
}
else {
return Single.just(temp)
}
}
Lastly, you aren't properly canceling your network request in your getRepo(_:) method. It should end with return Disposables.create { task.cancel() }
I suggest you read up more on Disposables.
Related
I want to fetch a data from three different APIs, and then save it in a database. Therefore, data from each query should be separated after the operation.
How to do it with RxSwift? Zip? In my example I'm using only two URLs, but it's just example.
QueryService:
import Foundation
import RxSwift
class QueryService {
let albumsURL = URL(string: "https://jsonplaceholder.typicode.com/albums")!
func fetchAlbums() -> Observable<[Album]> {
return Observable.create { observer -> Disposable in
let task = URLSession.shared.dataTask(with: self.albumsURL) { data, _, _ in
guard let data = data else {
observer.onError(NSError(domain: "", code: -1, userInfo: nil))
return
}
do {
let albums = try JSONDecoder().decode([Album].self, from: data)
observer.onNext(albums)
} catch {
observer.onError(error)
}
}
task.resume()
return Disposables.create{
task.cancel()
}
}
}
func fetchUsers() -> Observable<[User]> {
return Observable.create { observer -> Disposable in
let task = URLSession.shared.dataTask(with: URL(string: "https://jsonplaceholder.typicode.com/users")!) { data, _, _ in
guard let data = data else {
observer.onError(NSError(domain: "", code: -1, userInfo: nil))
return
}
do {
let users = try JSONDecoder().decode([User].self, from: data)
observer.onNext(users)
} catch {
observer.onError(error)
}
}
task.resume()
return Disposables.create{
task.cancel()
}
}
}
}
I'm assuming you're trying to execute two tasks in parallel and want to reach their results from a single observable.
If this is the case, your code should be like this:
Observable.zip(service.fetchAlbums(), service.fetchUsers())
.subscribe(onNext: { (albums, users) in
print(albums)
print(users)
})
.disposed(by: self.disposeBag)
I am working on a similar feature to 'liking/unliking a post'.
I have an MVVM architecture as;
struct MyStructModel {
var isLiked: Bool? = false
}
class MyStructView {
var isLiked: Bool
init(myStructModel: MyStructModel) {
self.isLiked = myStructModel.isLiked ?? false
}
}
I successfully get the value of whether the post is liked or not here;
func isPostLiked(documentID: String, completion: #escaping (Bool) -> Void) {
guard let authID = auth.id else { return }
let query = reference(to: .users).document(authID).collection("liked").document(documentID)
query.getDocument { (snapshot, error) in
if error != nil {
print(error as Any)
return
}
guard let data = snapshot?.data() else { return }
if let value = data["isLiked"] as? Bool {
completion(value)
} else {
completion(false)
}
}
}
func retrieveReviews(completion: #escaping([MyStructModel]) -> ()) {
var posts = [MyStructModel]()
let query = reference(to: .posts).order(by: "createdAt", descending: true)
query.getDocuments { (snapshot, error) in
if error != nil {
print(error as Any)
return
}
guard let snapshotDocuments = snapshot?.documents else { return }
for document in snapshotDocuments {
if var post = try? JSONDecoder().decodeQuery(MyStructModel.self, fromJSONObject: document.decode()) {
// isLiked is nil here...
self.isPostLiked(documentID: post.documentID!) { (isLiked) in
post.isLiked = isLiked
print("MODEL SAYS: \(post.isLiked!)")
// isLiked is correct value here...
}
posts.append(post)
}
completion(posts)
}
}
}
However, when it gets to my cell the value is still nil.
Adding Cell Code:
var post: MyStructView? {
didSet {
guard let post = post else { return }
print(post.isLiked!)
}
}
Your isLiked property is likely nil in your cells because the retrieveReviews function doesn't wait for the isPostLiked function to complete before completing itself.
You could easily solve this issue by using DispatchGroups. This would allow you to make sure all of your Posts have their isLiked value properly set before being inserted in the array, and then simply use the DispatchGroup's notify block to return all the loaded posts via the completion handler:
func retrieveReviews(completion: #escaping([MyStructModel]) -> ()) {
var posts = [MyStructModel]()
let query = reference(to: .posts).order(by: "createdAt", descending: true)
query.getDocuments { [weak self] (snapshot, error) in
guard let self = self else { return }
if error != nil {
return
}
guard let documents = snapshot?.documents else { return }
let dispatchGroup = DispatchGroup()
for document in documents {
dispatchGroup.enter()
if var post = try? JSONDecoder().decodeQuery(MyStructModel.self, fromJSONObject: document.decode()) {
self.isPostLiked(documentID: post.documentID!) { isLiked in
post.isLiked = isLiked
posts.append(post)
dispatchGroup.leave()
}
}
}
dispatchGroup.notify(queue: .main) {
completion(posts)
}
}
}
What am I doing wrong? How do I get the Single from the closure?
How can I get value from Alamofire.request?
func loadImageName(url: URL) -> Single<String> {
let data = try? Data(contentsOf: url)
guard let query = data else {
return .error(Error.notFound)
}
...
return Single.deferred {
Alamofire.request(request).responseJSON {
if let error = $0.error {
return Single<String>.error(error)
}
return Single<String>.just(result)
}
}
}
In this case you'll want Single.create.
This takes a block, which has a single argument. This argument is a function that you can call to pass a SingleEvent, i.e. either a .success(Element) (where Element is String in your case) or an .error.
The block must return a Disposable. You can construct a Disposable that will do additional work when it gets disposed. In the context of network requests, it makes sense to cancel the request.
func loadImageName(url: URL) -> Single<String> {
let data = try? Data(contentsOf: url)
guard let query = data else {
return .error(Error.notFound)
}
// ...
Single.create { single in
let request = Alamofire.request(request).responseJSON {
if let error = $0.error {
return single(.error(error))
}
return single(.success(result))
}
return Disposables.create { request.cancel() }
}
}
I am trying to load data from a GET request using Alamofire library in swift and cannot append data from the requests. I am trying to populate an array of orders to load into a UITableView.
I have tried a few various ways of solving this issue but nothing is working for me. I have commented out the method I tried because with 2 separate calls to fetchAll...Orders and the second call always overwrites the first and then the tableView is loaded with missing items.
class DrinkOrdersTableViewController: UITableViewController {
var orders: [Order] = []
override func viewDidLoad() {
super.viewDidLoad()
navigationItem.title = "Current Orders"
}
override func viewWillAppear(_ animated: Bool) {
// fetchAllBeerOrders { orders in
// self.orders = orders!
// //print("Beer fetch: ", self.orders)
// self.tableView.reloadData()
// }
// fetchAllCocktailOrders { orders in
// self.orders = orders!
// //print("Cocktail fetch: ", self.orders)
// self.tableView.reloadData()
// }
fetchAllBeerOrders { orders in
self.orders.append(orders)
self.tableView.reloadData()
}
fetchAllCocktailOrders { orders in
self.orders.append(orders)
self.tableView.reloadData()
}
}
private func fetchAllCocktailOrders(completion: #escaping([Order]?) -> Void) {
Alamofire.request("http://127.0.0.1:4000/orders", method: .get)
.validate()
.responseJSON { response in
guard response.result.isSuccess else { return completion(nil) }
guard let rawInventory = response.result.value as? [[String: Any]?] else { return completion(nil) }
let currentOrders = rawInventory.compactMap { ordersDict -> Order? in
guard let orderId = ordersDict!["id"] as? String,
let orderStatus = ordersDict!["status"] as? String,
var pizza = ordersDict!["cocktail"] as? [String: Any] else { return nil }
pizza["image"] = UIImage(named: pizza["image"] as! String)
return Order(
id: orderId,
pizza: Pizza(data: pizza),
status: OrderStatus(rawValue: orderStatus)!
)
}
completion(currentOrders)
}
}
private func fetchAllBeerOrders(completion: #escaping([Order]?) -> Void) {
Alamofire.request("http://127.0.0.1:4000/orders", method: .get)
.validate()
.responseJSON { response in
guard response.result.isSuccess else { return completion(nil) }
guard let rawInventory = response.result.value as? [[String: Any]?] else { return completion(nil) }
let currentOrders = rawInventory.compactMap { ordersDict -> Order? in
guard let orderId = ordersDict!["id"] as? String,
let orderStatus = ordersDict!["status"] as? String,
var pizza = ordersDict!["pizza"] as? [String: Any] else { return nil }
pizza["image"] = UIImage(named: pizza["image"] as! String)
return Order(
id: orderId,
pizza: Pizza(data: pizza),
status: OrderStatus(rawValue: orderStatus)!
)
}
completion(currentOrders)
}
}
As of right now I am getting this error with code above: Cannot convert value of type '[Order]?' to expected argument type 'Order'. The ideal outcome of this code is to have the data that is gathered from each GET request to append to the array of Orders. I have verified that the GET requests are working and giving back the correct data. Please Help :]
You declared orders of type [Order] and your fetch methods compilation blocks return [Order]?. As you can see, you cannot convert value of type [Order]? to expected argument type Order when you wrote self.orders.append(orders).
To fix these, put a guard unwrap in fetch method invocations.
fetchAllBeerOrders { orders in
guard let _orders = orders else { return }
self.orders.append(_orders)
self.tableView.reloadData()
}
fetchAllCocktailOrders { orders in
guard let _orders = orders else { return }
self.orders.append(_orders)
self.tableView.reloadData()
}
Now, you have a potential memory leak in your code. fetchAllBeerOrders and fetchAllCocktailOrders are async methods with compilation blocks. You cannot use a strong reference to self here. Use weak to avoid a memory leak, like:
fetchAllBeerOrders { [weak self] orders in
guard let _orders = orders else { return }
self?.orders.append(_orders)
self?.tableView.reloadData()
}
fetchAllCocktailOrders { [weak self] orders in
guard let _orders = orders else { return }
self?.orders.append(_orders)
self?.tableView.reloadData()
}
This question already has an answer here:
Return a string from a web scraping function in swift
(1 answer)
Closed 4 years ago.
How can I return a value within an if let statement to be further returned within a function? Here is the code:
func loadUrl(url:String) -> String {
DispatchQueue.global().async {
do {
let appUrl = URL(string:url)!
let data = try Data(contentsOf:appUrl)
let json = try JSONSerialization.jsonObject(with: data) as! [String:Any]
print("Test from do")
if let results = json["results"] as? [[String:Any]] {
print("Test from if let 1")
if let first = results[0] as? [String:Any] {
print("Test from if let 2")
var cityStateLocation = first["formatted_address"]!
return cityStateLocation
//What needs to be returned
}
}
DispatchQueue.main.async {
print("No Error")
}
} catch {
DispatchQueue.main.async {
print("Cannot connect to the server.")
}
}
}
}
What I would like to be able to do is take cityStateLocation and return it in the func, but because it is a part of an if let statement within an .async method I don't know how to do that. Could someone please explain?
EDIT: I need the return value of cityStateLocation to equal a variable in a separate function. Here is the separate function:
#IBAction func continueButton(_ sender: Any) {
var cityState:String
if locationSwitch.isOn == true {
print(location.latitude)
print(location.longitude)
let url = "https://maps.googleapis.com/maps/api/geocode/json?latlng=\(location.latitude),\(location.longitude)&result_type=locality&key=AIzaSyDI-ZacHyPbLchRhkoaUTDokwj--z_a_jk"
loadUrl(url: url)
cityState = loadUrl(url: url)
} else {
cityState = ""
}
CoreDataHandler.saveObject(locationLocality: cityState)
}
Edit 2: The main reason why the "duplicate answer" is not a duplicate is that my code needs to call the return of this function within a separate function then save it to Core Data. Also, my code is not using an array.
You could modify your function to include a closure. For instance:
func loadUrl(url: String, completionHandler: #escaping (_ location: String?) -> (Void)) {
And then, where you want to return it, you'd pass it in as such.
completionHandler(cityStateLocation)
I made it an optional so that, in your fail paths, you could return nil.
Then, where you call the function would change. Using trailing closure syntax, it could look like this:
loadUrl(url: "someurl.com/filepath.txt") { optionalLocation in
guard let nonOptionalLocation = optionalLocation else {
// Location was nil; Handle error case here
return
}
// Do something with your location here, like setting UI or something
}
This is a fairly common pattern when dealing with asynchronous activity, such as working with network calls.
The simplest (perhaps no the prettiest), way of doing this would simply be to declare and instantiate a variable above the dispatch queue. Then you can set the variable equal to whatever you want, within the dispatch queue, and return it afterwards. You can change the type of ret, so that it suits your needs more directly.
func loadUrl(url:String) -> String {
var ret = NSObject()
DispatchQueue.global().async {
do {
let appUrl = URL(string:url)!
let data = try Data(contentsOf:appUrl)
let json = try JSONSerialization.jsonObject(with: data) as! [String:Any]
print("Test from do")
if let results = json["results"] as? [[String:Any]] {
print("Test from if let 1")
if let first = results[0] as? [String:Any] {
print("Test from if let 2")
var cityStateLocation = first["formatted_address"]!
ret = cityStateLocation
//What needs to be returned
}
}
DispatchQueue.main.async {
print("No Error")
}
} catch {
DispatchQueue.main.async {
print("Cannot connect to the server.")
}
}
}
return ret
}
DispatchQueue.global().async will cause the coded included in the closure to be executed at some point the future, meaning you loadUrl function will return (almost) immediately.
What you need is some kind of callback which can be called when you have a result (AKA closure)
This is just another way to approach the problem, the difference between this and Josh's example is simply, I provide an additional closure to handle the errors
func loadUrl(url:String, complition: #escaping (String?) -> Void, fail: #escaping (Error) -> Void) {
DispatchQueue.global().async {
do {
let appUrl = URL(string:url)!
let data = try Data(contentsOf:appUrl)
let json = try JSONSerialization.jsonObject(with: data) as! [String:Any]
print("Test from do")
if let results = json["results"] as? [[String:Any]], !results.isEmpty {
print("Test from if let 1")
let first = results[0]
print("Test from if let 2")
if let cityStateLocation = first["formatted_address"] as? String {
complition(cityStateLocation)
} else {
complition(nil)
}
} else {
complition(nil)
}
} catch let error {
fail(error)
}
}
}
Which you might call using something like...
loadUrl(url: "your awesome url", complition: { (value) in
guard let value = value else {
// No value
return
}
// process value
}) { (error) in
// Handle error
}