I have an Observable Object class to store a forecast object for my app
The class looks like this:
final class ForecastData: ObservableObject {
#Published var forecast: DarkSkyResponse
public func getForecast(at location: CLLocation) {
let request = DarkSkyRequest(key: "KEYGOESHERE")
let point = DarkSkyRequest.Point(location.coordinate.latitude, location.coordinate.longitude)
guard let url = request.buildURL(point: point) else {
//Handle this better
preconditionFailure("Failed to construct URL")
}
let task = URLSession.shared.dataTask(with: url) {
data, response, error in
DispatchQueue.main.async {
guard let data = data else {
//Handle this better
fatalError("No Data Recieved")
}
guard let forecast = DarkSkyResponse(data: data) else {
//Handle this better
fatalError("Decoding Failed")
}
self.forecast = forecast
}
}
task.resume()
}
init() {
self.getForecast(at: CLLocation(latitude: 37.334987, longitude: -122.009066))
}
}
The first part simply generates a URL to access the API by. Then I start a URLSession which downloads the data and then parses it into a DarkSkyResponse object. Finally I set the #Published variable to the forecast object.
My problem is when I call the function in the initialiser, I get an error because the forecast property is not initialised. What is the best way to get around this? Where should I call the function?
By the way I am using this class in my SwiftUI View using an #ObservedObject property wrapper
Case1: use optional (and you need to handle it in View)
#Published var forecast: DarkSkyResponse?
Case2: use some default instance
#Published var forecast = DarkSkyResponse()
Both variants are equivalent and acceptable, so just by your preference.
Try this changes:
#Published var forecast: DarkSkyResponse!
and
init() {
super.init()
self.getForecast(at: CLLocation(latitude: 37.334987, longitude: -122.009066))
}
Related
I have two viewmodels, one contains the necessary data for the user, a classic api fetch, and the second viewmodel is also an api fetch, but I want to insert the data from the first into the second, whenever I try, it always outputs nil, although before that I ensure that it cannot output it because I know it exists because the fetch function was called first.
class UserPostViewModel: ObservableObject {
#Published var user: UserResponse?
#Published var phoneNumber:String = ""
#Published var firstName:String = ""
#Published var lastName:String = ""
#Published var selectedImage: UIImage?
#Published var normalizedMobileNumberField:String = ""
func createUser() {
guard let url = URL(string: "privateapi") else {
return
}
request.httpBody = try? JSONSerialization.data(withJSONObject: body, options: .fragmentsAllowed)
let task = URLSession.shared.dataTask(with: request) {data, response, error in
guard let data = data, error == nil else{
return
}
do {
let response = try? JSONDecoder().decode(UserResponse.self, from: data)
if self.normalizedMobileNumberField != "The number you enter is invalid." {
DispatchQueue.main.async {
self.user = response
if let userData = self.user {
print(userData.data.id)
}
}
} else {
print("You can't register application")
}
}
catch {
print(error)
}
}
task.resume()
}
}
This is the second one:
class GetTokenViewModel: ObservableObject {
#Published var tokenData: DataToken?
var userVM = UserPostViewModel()
func fetchData() {
let urlString = "privateapi/\(userVM.user.token)"
guard let url = URL(string: urlString) else { return }
var request = URLRequest(url:url)
URLSession.shared.dataTask(with: request) { data, response, error in
guard let data = data else {
return
}
do {
let decodedData = try JSONDecoder().decode(ResponseToken.self, from: data)
DispatchQueue.main.async{
self.tokenData = decodedData.data
print("TOKEN: \(self.tokenData?.token)")
}
} catch {
print("Error decoding JSON in gettoken: \(error)")
}
}.resume()
}
}
How to pass data from First ViewModel to the second?
I know that these codes have some error but I deleted every private information, but I believe that there is minimal code for understanding my question.
In SwiftUI, the View struct is equivalent to a view model but it is an immutable value type instead of an object that helps prevent consistency bugs. The property wrappers help it behave like an object. You pass data down the View struct hierarchy either with let if you want read access or #Binding var if you want write access. SwiftUI will track that these lets/vars are read in body and then body will be called whenever changes are detected. Transform the data as you pass it along from complex model types to simple value types.
#State declares a source of truth and #StateObject is when you need a reference type in an #State because you are doing something asynchronous or need to work around the limitations of closures in structs. Because these states are sources of truth you can't pass anything in because they won't be able to detect changes the same way the View struct can with let or #Binding var.
The best way to call web API in SwiftUI now is .task and .task(id:). The task will start when the view appears, cancelled if it disappears, or restarted if the id changes. This can completely remove the need for an object.
Language:Swift
Hello, I'd like some help in resolving an error being thrown when I try to retrieve data from an Apollo GraphQL request that I'm making. The API in use is the AniList API utilizing GraphQL.
Here's what I've tried:
In my model I'm making the Apollo GraphQL query inside of a search() function. I want to then use the Codable protocol to fill an array of anime objects. Currently it's setup to return just for 1 anime object. I was planning on using this anime list as a data set for TableView later. I wanted to take small steps so my current goal is to at least get the Codable protocol to work and return the response data to an anime Struct object.
The documentation for Apollo shows how to get individual fields but when I try to get the corresponding fields from my response , I don't even have the option.
func search(){
Network.shared.apollo.fetch(query: AnisearchQuery()){ result in
guard let data = try? result.get().data else { return }
var topData:APIResponse?
do{
topData = JSONDecoder().decode(APIResponse.self, from: data.self)
}catch{
}
}
}
Here are the data structures that I've set up as a representation of the JSON data I expect to receive with respect to the hierarchy it is laid out in the response.
struct APIResponse:Codable{
let data:data
}
struct data:Codable{
let Page:page
let media:media
}
struct media:Codable{
let animeResults:anime
}
struct anime:Codable{
var romaji:String
var english: String
var native:String
var episodes:Int
var duration:Int
var medium:String
}
Here is the error in question.
"Cannot convert value of type 'AnisearchQuery.Data' to expected argument type 'Data'". This is generated by this line of code
topData = JSONDecoder().decode(APIResponse.self, from: data.self)
For further context , AnisearchQuery.Data is generated in response to the query I created for the codgen.
Here's what the data would look like in JSON format
This is the setup of the query:
query anisearch($page:Int, $perPage:Int, $search:String){
Page (page:$page, perPage:$perPage){
pageInfo {
total
currentPage
lastPage
hasNextPage
perPage
}
media(search:$search){
title{
romaji
english
native
}
episodes
duration
coverImage{
medium
}
}
}
}
Here's the Data object in the API.swift file:
public struct Data: GraphQLSelectionSet {
public static let possibleTypes: [String] = ["Query"]
public static var selections: [GraphQLSelection] {
return [
GraphQLField("Page", arguments: ["page": GraphQLVariable("page"), "perPage": GraphQLVariable("perPage")], type: .object(Page.selections)),
]
}
I'd be open to any alternative methods as to getting this task done or perhaps fixes to the error being thrown.
Many thanks in advance.
Inefficient Workaround
var animeCollection:SearchAnimeQuery.Data?
var media:[SearchAnimeQuery.Data.Page.Medium]?
var filteredData:[SearchAnimeQuery.Data.Page.Medium] = []
func loadData(search:String = "") {
if !search.isEmpty{
Network.shared.apollo.fetch(query: SearchAnimeQuery(search: search)){
[weak self] result in
//Make Sure ViewController Has not been deallocated
guard let self = self else{
return
}
/*defer {
}*/
switch result {
case .success(let graphQLResult):
if let animeData = graphQLResult.data {
DispatchQueue.main.async {
self.animeCollection = animeData
self.media = self.animeCollection?.page?.media as! [SearchAnimeQuery.Data.Page.Medium]
self.filteredData = self.media!
self.tableView.reloadData()
}
}
if let errors = graphQLResult.errors {
let message = errors
.map { $0.localizedDescription }
.joined(separator: "\n")
print(message)
}
case .failure(let error):
print(error.localizedDescription)
}
}
}
}
Currently im creating application which parses JSON from my server. From server I can receive array with JSON models.
Data from this array must be populated in table View.
My question Is simple: where to store decoded array from server, if I want to access it from many viewControllers in my application?
Here is my JSON model, which coming from server.
import Foundation
struct MyModel: Codable {
var settings: Test?
var provider: [Provider]
}
extension MyModel {
struct setting: Codable {
var name: String
var time: Int
}
}
here is how I am decoding it
import Foundation
enum GetResourcesRequest<ResourceType> {
case success([ResourceType])
case failure
}
struct ResourceRequest<ResourceType> where ResourceType: Codable {
var startURL = "https://myurl/api/"
var resourceURL: URL
init(resourcePath: String) {
guard let resourceURL = URL(string: startURL) else {
fatalError()
}
self.resourceURL = resourceURL.appendingPathComponent(resourcePath)
}
func fetchData(completion: #escaping
(GetResourcesRequest<ResourceType>) -> Void ) {
URLSession.shared.dataTask(with: resourceURL) { data, _ , _ in
guard let data = data else { completion(.failure)
return }
let decoder = JSONDecoder()
if let jsonData = try? decoder.decode([ResourceType].self, from: data) {
completion(.success(jsonData))
} else {
completion(.failure)
}
}.resume()
}
}
This is an example of CategoriesProvider. It just stores categories in-memory and you can use them across the app. It is not the best way to do it and not the best architecture, but it is simple to get started.
class CategoriesProvider {
static let shared = CategoriesProvider()
private(set) var categories: [Category]?
private let categoryRequest = ResourceRequest<Category>(resourcePath: "categories")
private let dataTask: URLSessionDataTask?
private init() {}
func fetchData(completion: #escaping (([Category]?) -> Void)) {
guard categories == nil else {
completion(categories)
return
}
dataTask?.cancel()
dataTask = categoryRequest.fetchData { [weak self] categoryResult in
var fetchedCategories: [Category]?
switch categoryResult {
case .failure:
print("error")
case .success(let categories):
fetchedCategories = categories
}
DispatchQueue.main.async {
self?.categories = fetchedCategories
completion(fetchedCategories)
}
}
}
}
I suggest using URLSessionDataTask in order to cancel a previous task. It could happen when you call fetchData several times one after another. You have to modify your ResourceRequest and return value of URLSession.shared.dataTask(...)
Here more details about data task https://www.raywenderlich.com/3244963-urlsession-tutorial-getting-started#toc-anchor-004 (DataTask and DownloadTask)
Now you can fetch categories in CategoriesViewController in this way:
private func loadTableViewData() {
CategoriesProvider.shared.fetchData { [weak self] categories in
guard let self = self, let categories = categories else { return }
self.categories = categories
self.tableView.reloadData()
}
}
In the other view controllers, you can do the same but can check for the 'categories' before making a fetch.
if let categories = CategoriesProvider.shared.categories {
// do something
} else {
CategoriesProvider.shared.fetchData { [weak self] categories in
// do something
}
}
If you really want to avoid duplicate load data() calls, your simplest option would be to cache the data on disk (CoreData, Realm, File, etc.) after parsing it the first time.
Then every ViewController that needs the data, can just query your storage system.
Of course the downside of this approach is the extra code you'll have to write to manage the coherency of your data to make sure it's properly managed across your app.
make a global dictionary array outside any class to access it on every viewcontroller.
I'm Learning Swift development for IOS and encountered a design problem in my simple Project. I have a pickerView set up so that everytime user selects a value, different information from the Json is displayed and it works just fine.
However, in my current design the data gets parsed/fetched again everytime the user selects a new value from the pickerview, what I want to do is to collect the data once and then just loop through the same data based on the users selection. My guess is that i need to separate the function to load the data and the function/code to actually do the looping and populate the labels. But I can't seem to find any way to solve it, when i try to return something from my loadData function I get problems with the returns already used inside the closure statements inside the function.
Hopefully you guys understand my question!
The selectedName variable equals the users selected value from the pickerView.
The function loadData gets run inside the pickerView "didselectrow" function.
func loadData() {
let jsonUrlString = "Here I have my Json URL"
guard let url = URL(string: jsonUrlString) else
{ return }
URLSession.shared.dataTask(with: url) { (data, response, err) in
guard let data = data else { return }
do { let myPlayerInfos = try
JSONDecoder().decode(Stats.self, from: data)
DispatchQueue.main.async {
for item in myPlayerInfos.elements! {
if item.web_name == self.selectedName{
self.nameLabel.text = "Name:\t \t \(item.first_name!) \(item.second_name!)"
} else {}
}
}
} catch let jsonErr {
print("Error serializing json:", jsonErr)
}
}.resume()
}//end function loaddata
And for reference, the Stats struct:
struct Stats: Decodable {
let phases: [playerPhases]?
let elements: [playerElements]?
}
struct playerPhases: Decodable{
let id: Int?
}
struct playerElements: Decodable {
let id: Int?
let photo: String?
let first_name: String?
let second_name: String?
}
I am trying to get an array of temperatures in a given time period from an API in JSON format. I was able to retrieve the array through a completion handler but I can't save it to another variable outside the function call (one that uses completion handler). Here is my code. Please see the commented area.
class WeatherGetter {
func getWeather(_ zip: String, startdate: String, enddate: String, completion: #escaping (([[Double]]) -> Void)) {
// This is a pretty simple networking task, so the shared session will do.
let session = URLSession.shared
let string = "api address"
let url = URL(string: string)
var weatherRequestURL = URLRequest(url:url! as URL)
weatherRequestURL.httpMethod = "GET"
// The data task retrieves the data.
let dataTask = session.dataTask(with: weatherRequestURL) {
(data, response, error) -> Void in
if let error = error {
// Case 1: Error
// We got some kind of error while trying to get data from the server.
print("Error:\n\(error)")
}
else {
// Case 2: Success
// We got a response from the server!
do {
var temps = [Double]()
var winds = [Double]()
let weather = try JSON(data: data!)
let conditions1 = weather["data"]
let conditions2 = conditions1["weather"]
let count = conditions2.count
for i in 0...count-1 {
let conditions3 = conditions2[i]
let conditions4 = conditions3["hourly"]
let count2 = conditions4.count
for j in 0...count2-1 {
let conditions5 = conditions4[j]
let tempF = conditions5["tempF"].doubleValue
let windspeed = conditions5["windspeedKmph"].doubleValue
temps.append(tempF)
winds.append(windspeed)
}
}
completion([temps, winds])
}
catch let jsonError as NSError {
// An error occurred while trying to convert the data into a Swift dictionary.
print("JSON error description: \(jsonError.description)")
}
}
}
// The data task is set up...launch it!
dataTask.resume()
}
}
I am calling this method from my view controller class. Here is the code.
override func viewDidLoad() {
super.viewDidLoad()
let weather = WeatherGetter()
weather.getWeather("13323", startdate: "2016-10-01", enddate: "2017-04-30") { (weatherhandler: [[Double]]) in
//It prints out the correct array here
print(weatherhandler[0])
weatherData = weatherhandler[0]
}
//Here it prints out an empty array
print(weatherData)
}
The issue is that API takes some time to return the data, when the data is return the "Completion Listener" is called and it goes inside the "getWeather" method implementation, where it prints the data of array. But when your outside print method is called the API hasn't returned the data yet. So it shows empty array. If you will try to print the data form "weatherData" object after sometime it will work.
The best way I can suggest you is to update your UI with the data inside the "getWeather" method implementation like this:
override func viewDidLoad() {
super.viewDidLoad()
let weather = WeatherGetter()
weather.getWeather("13323", startdate: "2016-10-01", enddate: "2017-04-30") { (weatherhandler: [[Double]]) in
//It prints out the correct array here
print(weatherhandler[0])
weatherData = weatherhandler[0]
// Update your UI here.
}
//Here it prints out an empty array
print(weatherData)
}
It isn't an error, when your controller get loaded the array is still empty because your getWeather is still doing its thing (meaning accessing the api, decode the json) when it finishes the callback will have data to return to your controller.
For example if you were using a tableView, you will have reloadData() to refresh the UI, after you assign data to weatherData
Or you could place a property Observer as you declaring your weatherData property.
var weatherData:[Double]? = nil {
didSet {
guard let data = weatherData else { return }
// now you could do soemthing with the data, to populate your UI
}
}
now after the data is assigned to wheaterData, didSet will be called.
Hope that helps, and also place your jsonParsing logic into a `struct :)