I know this question is asked a lot, but I can't figure out how to apply any answers to my program. Sorry in advance this async stuff makes absolutely zero sense to me.
Basically, I have a button in SwiftUI that, when pressed, calls a function that makes two API calls to Google Sheets using Alamofire and GoogleSignIn.
Button("Search") {
if fullName != "" {
print(SheetsAPI.nameSearch(name: fullName, user: vm.getUser()) ?? "Error")
}
}
This function should return the values of some cells on success or nil on an error. However, it only ever prints out "Error". Here is the function code.
static func nameSearch<S: StringProtocol>(name: S, advisory: S = "", user: GIDGoogleUser?) -> [String]? {
let name = String(name)
let advisory = String(advisory)
let writeRange = "'App Control'!A2:C2"
let readRange = "'App Control'!A4:V4"
// This function can only ever run when user is logged in, ! should be fine?
let user = user!
let parameters: [String: Any] = [
"range": writeRange,
"values": [
[
name,
nil,
advisory
]
]
]
// What I want to be returned
var data: [String]?
// Google Identity said use this wrapper so that the OAuth tokens refresh
user.authentication.do { authentication, error in
guard error == nil else { return }
guard let authentication = authentication else { return }
// Get the access token to attach it to a REST or gRPC request.
let token = authentication.accessToken
let headers: HTTPHeaders = ["Authorization": "Bearer \(token)"]
AF.request("url", method: .put, parameters: parameters, encoding: JSONEncoding.default, headers: headers).responseString { response in
switch response.result {
case .success:
// I assume there is a better way to make two API calls...
AF.request("anotherURL", headers: headers).responseDecodable(of: NameResponseModel.self) { response2 in
switch response2.result {
case .success:
guard let responseData = response2.value else { return }
data = responseData.values[0]
// print(responseData.values[0]) works fine
case .failure:
print(response2.error ?? "Unknown error.")
data = nil
}
}
case .failure:
print(response.error ?? "Unknown error.")
data = nil
}
}
}
// Always returns nil, "Unknown error." never printed
return data
}
The model struct for my second AF request:
struct NameResponseModel: Decodable { let values: [[String]] }
An example API response for the second AF request:
{
"range": "'App Control'!A4:V4",
"majorDimension": "ROWS",
"values": [
[
"Bob Jones",
"A1234",
"Cathy Jones",
"1234 N. Street St. City, State 12345"
]
]
}
I saw stuff about your own callback function as a function parameter (or something along those lines) to handle this, but I was completely lost. I also looked at Swift async/await, but I don't know how that works with callback functions. Xcode had the option to refactor user.authentication.do { authentication, error in to let authentication = try await user.authentication.do(), but it threw a missing parameter error (the closure it previously had).
EDIT: user.authentication.do also returns void--another reason the refactor didn't work (I think).
There is probably a much more elegant way to do all of this so excuse the possibly atrocious way I did it.
Here is the link to Google Identity Wrapper info.
Thanks in advance for your help.
Solved my own problem.
It appears (according to Apple's async/await intro video) that when you have an unsupported callback that you need to run asynchronously, you wrap it in something called a Continuation, which allows you to manually resume the function on the thread, whether throwing or returning.
So using that code allows you to run the Google Identity token refresh with async/await.
private static func auth(_ user: GIDGoogleUser) async throws -> GIDAuthentication? {
typealias AuthContinuation = CheckedContinuation<GIDAuthentication?, Error>
return try await withCheckedThrowingContinuation { (continuation: AuthContinuation) in
user.authentication.do { authentication, error in
if let error = error {
continuation.resume(throwing: error)
} else {
continuation.resume(returning: authentication)
}
}
}
}
static func search(user: GIDGoogleUser) async throws {
// some code
guard let authentication = try await auth(user) else { ... }
// some code
}
I then ran that before using Alamofire's built-in async/await functionality for each request (here's one).
let dataTask = AF.request(...).serializingDecodable(NameResponseModel.self)
let response = try await dataTask.value
return response.values[0]
Related
This question already has answers here:
Returning data from async call in Swift function
(13 answers)
Closed last year.
I'm new at Swift and that's why i need your help. So I have a function which should send request and return a value
func getAnswer() -> String? {
var answer: String?
guard let url = URL(string: "https://8ball.delegator.com/magic/JSON/_") else { return nil }
URLSession.shared.dataTask(with: url) { data, response, error in
guard let data = data, error == nil else {
return
}
guard let response = response as? HTTPURLResponse else { return }
guard response.statusCode == 200 else { return }
do {
let model = try JSONDecoder().decode(Answer.self, from: data)
DispatchQueue.main.async {
answer = model.magic.answer
}
} catch let error {
fatalError(error.localizedDescription)
}
}.resume()
return answer
}
but it always returns nil.
I suppose problem is here
DispatchQueue.main.async {
answer = model.magic.answer
}
How can I fix it?
In order to know what is happening here, you need to learn about #escaping functions in swift, here is some link1 together with taking function as another functions parameter link2 written in part "Function Types as Parameter Types" , closures in Swift link3 and
Here is what is happening simplified and explained step by step :
you call getAnswer()
variable answer gets initialized with value nil by declaring answer: String?
URLSession.shared.dataTask is called and it is taking as an argument another function - closure (Data?, URLResponse?, Error?) -> Void . Also URLSession.shared.dataTask is executed on different thread and is not returning yet, but will return right after it receives response from server, which can take any time (but usually milliseconds) and will basically happen after your getAnswer() function is returning value.
your getAnswer() immediately returns value of answer which is currently nil
if you get any data from server, or server could not be reached, your URLSession.shared.dataTask function executes your code in closure. This is the code it will execute:
guard let data = data, error == nil else {
return
}
guard let response = response as? HTTPURLResponse else { return }
guard response.statusCode == 200 else { return }
do {
let model = try JSONDecoder().decode(Answer.self, from: data)
DispatchQueue.main.async {
answer = model.magic.answer
}
} catch let error {
fatalError(error.localizedDescription)
}
Your problem lies in how swift executes closures. When you call
URLSession.shared.dataTask(with: url) {
// Closure code here
}
return answer
Your "Closure code here" doesn't get called until the endpoint "https://8ball.delegator.com/magic/JSON/_" actually gives a response. However, you've promised swift that your function will return an optional string immediately after the serial code of your function has completed. For this reason, by the time your "Closure code here" has run, and your "answer" variable has been updated with the correct value, your function is long gone, and has already returned a value (which in this case is whatever you've set it to at the beginning - nil).
You can fix this issue in one of two ways.
Swift's new concurrency system
By defining your own closure.
Swift's new concurrency system
You can define your function as async, meaning that the function won't have to return a value in serial, as follows.
enum GetAnswerError: Error {
case invalidURL
}
func getAnswer() async throws -> String {
var answer: String?
guard let url = URL(string: "https://8ball.delegator.com/magic/JSON/_") else {
throw GetAnswerError.invalidURL
}
// Your function will suspend here and probably be moved to a different thread. It will resume once a response has been received from the endpoint.
let (data, _) = try await URLSession.shared.dataTask(with: url)
let parsedData = try JSONDecoder().decode(Answer.self, from: data)
return parsedData.magic.answer
}
When you call this function, you'll have to do so from an environment which swift can suspend. This means you'll call the function from either another async function like so
func anotherFunction() async throws -> Bool {
let answer = try await getAnswer()
// Run some code here
return answer == "YES" // Return some useful value
}
or from a Task object like so
Task {
// Note that because the function getAnswer() can throw errors, you'll have to handle them when you call the function. In this case, I'm handling them by using try?, which will simply set answer to nil if an error is thrown.
let answer = try? await getAnswer()
}
Note that when you call code in a task, you must be using the return value's from within the scope of the task. If you try to do something like this
func getAnswerTheSecond() -> String? {
var answer: String? = nil
Task {
let receivedAnswer = try? await getAnswer()
answer = receivedAnswer
}
return answer
}
You'll just end up back where you started, where swift immediately returns the nil value because your code is ran in serial. To fix this, run the relevant code on the "answer" from wherever it is needed within the task. If you are using the "answer" to update a SwiftUI view that might look like this.
struct ContentView: View {
#State var answer: String = ""
// This is the function that I've written earlier
func getAnswer() async throws -> String {
// Make URL Request
// Return the value
}
var body: some View {
Text(self.answer)
.onAppear{
Task{
let result = try? await self.getAnswer()
self.answer = result
}
}
}
}
Defining your own closure
You can define your own closure to handle the URL response; however, because of swift's new concurrency framework, this is probably not the right way to go.
If you'd like to go this way, do a google search for "Swift closures", and you'll find what you need.
Not familiar enough with AWS, but I have some Codable models I need to initialize from AWS. I'm getting JSON result from AWSTask.result (which is AnyObject). I'm trying to avoid creating Data from Dictionaty and back to a struct (to be able to use Codable).
I tied to use AWSNetworkingHTTPResponseInterceptor, but it was never got called and I couldn't find any example of using it.
self.getGatewayClient { (apiGatewayClient: AWSAPIGatewayClient?) in
let queryParameters = ...
let headerParameters = ...
apiGatewayClient?.invokeHTTPRequest(
"GET",
urlString: "/path",
pathParameters: [:],
queryParameters: queryParameters,
headerParameters: headerParameters,
body: nil,
responseClass: nil
).continueWith { (task: AWSTask<AnyObject>) -> Any? in
if let data = task... { // Get response as Data type??
}
if let result = task.result as? [String: Any] {
// Thanks, but I have a Codable, so I'll just take the data thank you.
}
return task
}
}
AWS's AWSAPIGatewayClient has two functions, one is: invokeHTTPRequest (which was what was used). There is another one called invoke, which returns data. It takes a AWSAPIGatewayRequest request:
func someTask(completion: #escaping (String?) -> ()) {
self.getGatewayClient { (apiGatewayClient: AWSAPIGatewayClient?) in
let request = AWSAPIGatewayRequest(httpMethod: "GET",
urlString: "/path",
queryParameters: queryParameters,
headerParameters: headerParameters,
httpBody: nil)
apiGatewayClient?.invoke(request).continueOnSuccessWith { response in
if let data = response.result?.responseData {
// Init Codable using data
}
}
}
}
Hello new to Swift and Alamofire,
The issue i'm having is when I call this fetchAllUsers() the code will return the empty users array and after it's done executing it will go inside the AF.request closure and execute the rest.
I've done some research and I was wondering is this is caused by Alamofire being an Async function.
Any suggestions?
func fetchAllUsers() -> [User] {
var users = [User]()
let allUsersUrl = baseUrl + "users/"
if let url = URL(string: allUsersUrl) {
AF.request(url).response { response in
if let data = response.data {
users = self.parse(json: data)
}
}
}
return users
}
You need to handle the asynchrony in some way. This this means passing a completion handler for the types you need. Other times it means you wrap it in other async structures, like promises or a publisher (which Alamofire also provides).
In you case, I'd suggest making your User type Decodable and allow Alamofire to do the decoding for you.
func fetchAllUsers(completionHandler: #escaping ([User]) -> Void) {
let allUsersUrl = baseUrl + "users/"
if let url = URL(string: allUsersUrl) {
AF.request(url).responseDecodable(of: [User].self) { response in
if let users = response.value {
completionHandler(users)
}
}
}
}
However, I would suggest returning the full Result from the response rather than just the [User] value, otherwise you'll miss any errors that occur.
There is not enough documents about firebase functions.httpsCallable("findItems").call() usage. I have deployed functions on firebase:
exports.findItems = functions.https.onCall((data, context) => {
// Grab the long parameter.
functions.logger.log(data.long, typeof data.long);
functions.logger.log(data.lat, typeof data.lat);
const long = parseFloat(data.long);
const lat = parseFloat(data.lat);
functions.logger.log(long, typeof long);
functions.logger.log(lat, typeof lat);
//...
}
I make a request in swift using functions.httpsCallable("findItems").call() but the log always says there is no correct parameters:
functions.httpsCallable("findItems").call(["lat": userLocation?.latitude, "long": userLocation?.longitude]) { (result, error) in
if let error = error as NSError? {
if error.domain == FunctionsErrorDomain {
let code = FunctionsErrorCode(rawValue: error.code)
let message = error.localizedDescription
let details = error.userInfo[FunctionsErrorDetailsKey]
}
// ...
print(error)
return
}
print(result?.data)
do{
let json = try JSONDecoder().decode([ItemLocation].self, from:result?.data as! Data)
print(json)
}catch{
}
// if let text = (result?.data as? [String: Any])?
//(result?.data as? [String: Any])?["text"] as? String {
//self.resultField.text = text
}
You can find the offcial documents from : https://firebase.google.com/docs/functions/callable
-----Update---------
I have tried everything by debugging and the passed parameters are always undefined but I follow every step on the official doc.
I have made changes and use onCall but it still doesn't work?
You are mixing up HTTP functions with callable functions. Your client code is trying to call a callable function, but your function itself is defined as an HTTP function. This won't work at all. You should review the documentation for callable function and use functions.https.onCall instead of functions.https.onRequest to define your function. They are completely different APIs.
I have a function that calls 2 types of api requests to get a bunch of data i need in my app. In the function I make a request for locations, then for each location in the response I make a different request to get details of that specific location. (ex. if request 1 returns 20 locations, my second request is called 20 times, once for each location)
My function code here:
func requestAndCombineGData(location: CLLocation, radius: Int) {
// Clears map of markers
self.mapView.clear()
// Calls 'Nearby Search' request
googleClient.getGooglePlacesData(location: location, withinMeters: radius) { (response) in
print("Made Nearby Search request. Returned response here:", response)
// loops through each result from the above Nearby Request response
for location in response.results {
// Calls 'Place Details' request
self.googleClient.getGooglePlacesDetailsData(place_id: location.place_id) { (detailsResponse) in
print("GMV returned - detailsResponse.result - ", detailsResponse.result)
}
}
}
}
Request functions I reference above are here:
func getGooglePlacesData(location: CLLocation, withinMeters radius: Int, using completionHandler: #escaping (GooglePlacesResponse) -> ()) {
for category in categoriesArray {
let url = googlePlacesNearbyDataURL(forKey: googlePlacesKey, location: location, radius: radius, type: category)
let task = session.dataTask(with: url) { (responseData, _, error) in
if let error = error {
print(error.localizedDescription)
return
}
guard let data = responseData, let response = try? JSONDecoder().decode(GooglePlacesResponse.self, from: data) else {
print("Could not decode JSON response")
completionHandler(GooglePlacesResponse(results:[]))
return
}
if response.results.isEmpty {
print("GC - response returned empty", response)
} else {
print("GC - response contained content", response)
completionHandler(response)
}
}
task.resume()
}
}
func getGooglePlacesDetailsData(place_id: String, using completionHandler: #escaping (GooglePlacesDetailsResponse) -> ()) {
let url = googlePlacesDetailsURL(forKey: googlePlacesKey, place_ID: place_id)
let task = session.dataTask(with: url) { (responseData, _, error) in
if let error = error {
print(error.localizedDescription)
return
}
guard let data = responseData, let detailsResponse = try? JSONDecoder().decode(GooglePlacesDetailsResponse.self, from: data) else {
print("Could not decode JSON response. responseData was: ", responseData)
return
}
print("GPD response - detailsResponse.result: ", detailsResponse.result)
completionHandler(detailsResponse)
}
task.resume()
}
After I get all the data im requesting (or even as the data is coming in) I would like to append it to an #EnvironmentObject (array) I have set up in my SceneDelegate.swift file. Im using the data in multiple places in my app so the #EnvironmentObject serves as a 'source of truth'.
I tried accomplishing this using the code below, but keep getting the error - "Publishing changes from background threads is not allowed; make sure to publish values from the main thread (via operators like receive(on:)) on model updates."
func requestAndCombineGData(location: CLLocation, radius: Int) {
// Clears map of markers
self.mapView.clear()
// Calls 'Nearby Search' request
googleClient.getGooglePlacesData(location: location, withinMeters: radius) { (response) in
print("Made Nearby Search request. Returned response here:", response)
// loops through each result from the above Nearby Request response
for location in response.results {
// Calls 'Place Details' request
self.googleClient.getGooglePlacesDetailsData(place_id: location.place_id) { (detailsResponse) in
print("GMV returned - detailsResponse.result - ", detailsResponse.result)
// THIS IS WHERE I TRY TO UPDATE MY #ENVIROMETOBJECT
self.venueData.venuesdataarray.append(detailsRespose.result)
}
}
}
}
I believe I need to make sure the requests complete THEN try to update my #EnvironmentObject, but I do not know how to do that.
EDIT - providing my VenueData struct as requested in comments:
struct VenueData : Identifiable {
var id = UUID()
var name : String
var geometry : Location?
var rating : String?
var price_level : String?
var types : [String]?
var formatted_address : String?
var formatted_phone_number : String?
var website : String?
var photo_reference : String?
enum CodingKeysDetails : String, CodingKey {
case geometry = "geometry"
case name = "name"
case rating = "rating"
case price_level = "price_level"
case types = "types"
case opening_hours = "opening_hours"
case formatted_address = "formatted_address"
case formatted_phone_number = "formatted_phone_number"
case website = "website"
}
// Location struct
struct Location : Codable {
var location : LatLong
enum CodingKeys : String, CodingKey {
case location = "location"
}
// LatLong struct
struct LatLong : Codable {
var latitude : Double
var longitude : Double
enum CodingKeys : String, CodingKey {
case latitude = "lat"
case longitude = "lng"
}
}
}
}
class VenueDataArray: ObservableObject {
#Published var venuesdataarray : [VenueData] = [
VenueData(name: "test_name")
]
}
Solution Edit - I tried using this snippet of code within my second api request and it solved my issue, although i do not understand why I need to do this
DispatchQueue.main.async {
self.venueData.venuesdataarray.append(RESPONSE_DETAILS_HERE)
}
Originally I had asked, Does anyone know how I can update my #EnvironmentObject after all the requests complete?
Does anyone know why the snippet I have above makes everything work?
Id just like to understand what im doing and maybe someone could learn something if they find this
I tried using this snippet of code within my second api request and it solved my issue, although i do not understand why I need to do this
DispatchQueue.main.async {
self.venueData.venuesdataarray.append(RESPONSE_DETAILS_HERE)
}
Originally I had asked, Does anyone know how I can update my #EnvironmentObject after all the requests complete?
Does anyone know why the snippet I have above makes everything work? Id just like to understand what im doing and maybe someone could learn something if they find this
There are several things that you cannot successfully do from a background thread. Some of them (like UIKit content changes) do not generate an error, but fail silently which is worse. You have the good fortune to have received a relatively specific error message.
The error message was that you couldn't publish changes from a background thread and needed to do that from the main thread.
Wrapping your append inside "DispatchQueue.main.async" makes that line of code run on the main thread.
That's it.
This could probably have been explained more concisely.