I am learning Swift/SwiftUI and I faced a problem. The Xcode's writing this:
"Expected to decode Dictionary<String, CurrencyData> but found an array instead."
Here's a code:
import Foundation
import SwiftUI
struct CurrencyData: Codable {
let r030: Int
let txt: String
let rate: Double
let cc: String
let exchangedate: String
}
typealias Currency = [String: CurrencyData]
import SwiftUI
class API: ObservableObject {
#Published var currencyCode: [String] = []
#Published var priceRate: [Double] = []
#Published var exchangeDate: [String] = []
init() {
fetchdata { (currency) in
switch currency {
case .success(let currency):
currency.forEach { (c) in
DispatchQueue.main.async {
self.currencyCode.append(c.value.cc)
self.priceRate.append(c.value.rate)
self.exchangeDate.append(c.value.exchangedate)
}
}
case(.failure(let error)):
print("Unable to featch the currencies data", error)
}
}
}
func fetchdata(completion: #escaping (Result<Currency,Error>) -> ()) {
guard let url = URL(string: "https://bank.gov.ua/NBUStatService/v1/statdirectory/exchange?json") else { return }
URLSession.shared.dataTask(with: url) { data, responce, error in
if let error = error {
completion(.failure(error))
return
}
guard let safeData = data else { return }
do {
let currency = try JSONDecoder().decode(Currency.self, from: safeData)
completion(.success(currency))
}
catch {
completion(.failure(error))
}
}
.resume()
}
}
Change the type to correctly decode what you receive ( an array obviously )
This should work, but we can't answer for sure since we have no idea of the data. An attached json sample could help.
typealias Currency = [CurrencyData]
Change the exchangeDate in your CurrencyData model to exchangedate which need to match exactly the same as api response. It was case sensitive.
Related
In my app I am using MVVM pattern.
Below is my Model.
struct NewsModel: Codable {
let status: String
let totalResults: Int
let articles: [Article]
}
struct Article: Codable {
let source: Source
let author: String?
let title: String
let articleDescription: String?
let url: String
let urlToImage: String?
let publishedAt: Date
let content: String?
enum CodingKeys: String, CodingKey {
case source, author, title
case articleDescription = "description"
case url, urlToImage, publishedAt, content
}
}
struct Source: Codable {
let id: String?
let name: String
}
Below is my ViewModel. Which is used for show the data from API.
struct NewsArticleViewModel {
let article: Article
var title:String {
return self.article.title
}
var publication:String {
return self.article.articleDescription!
}
var imageURL:String {
return self.article.urlToImage!
}
}
Below is my API request class.
class Webservice {
func getTopNews(completion: #escaping (([NewsModel]?) -> Void)) {
guard let url = URL(string: "https://newsapi.org/v2/top-headlines?country=us&category=business&apiKey=2bfee85c94e04fc998f65db51ec540bb") else {
fatalError("URL is not correct!!!")
}
URLSession.shared.dataTask(with: url) {
data, response, error in
guard let data = data, error == nil else {
DispatchQueue.main.async {
completion(nil)
}
return
}
let news = try? JSONDecoder().decode([NewsModel].self, from: data)
DispatchQueue.main.async {
completion(news)
}
}.resume()
}
}
After receiving response from my API I want to show it on screen. For this I added below ViewModel.
class NewsListViewModel: ObservableObject {
#Published var news: [NewsArticleViewModel] = [NewsArticleViewModel]()
func load() {
fetchNews()
}
private func fetchNews() {
Webservice().getTopNews {
news in
if let news = news {
//How to bind this data to NewsArticleViewModel and show it on UI?
}
}
}
}
Please let me know. What I have to write there for showing it on UI.
According to the documentation of newsapi.org your request will return one NewsModel object not an array. So change your Webservice class to:
class Webservice {
//Change the completion handler to return an array of Article
func getTopNews(completion: #escaping (([Article]?) -> Void)) {
guard let url = URL(string: "https://newsapi.org/v2/top-headlines?country=us&category=business&apiKey=2bfee85c94e04fc998f65db51ec540bb") else {
fatalError("URL is not correct!!!")
}
URLSession.shared.dataTask(with: url) {
data, response, error in
guard let data = data, error == nil else {
DispatchQueue.main.async {
completion(nil)
}
return
}
// decode to a single NewsModel object instead of an array
let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .iso8601
let news = try? decoder.decode(NewsModel.self, from: data)
DispatchQueue.main.async {
// completion with an optional array of Article
completion(news?.articles)
}
}.resume()
}
}
You would need to map those received values to NewsArticleViewModel types. For example:
Webservice().getTopNews { articles in
if let articles = articles {
self.news = articles.map{NewsArticleViewModel(article: $0)}
}
}
And remove let news: NewsModel from the NewsArticleViewModel struct as it is not needed.
Edit:
It seems:
let publishedAt: Date
is throwing an error. Jsondecoder fails to interpret the string to a date. Change your Webservice. I´ve updated it in my answer.
You could remove the legacy MVVM pattern and do it in proper SwiftUI like this:
struct ContentView: View {
#State private var articles = [Article]()
var body: some View {
NavigationView {
List(articles) { article in
Text(article.title)
}
.navigationTitle("Articles")
}
.task {
do {
let url = URL(string: "https://newsapi.org/v2/top-headlines?country=us&category=business&apiKey=2bfee85c94e04fc998f65db51ec540bb")!
let (data, _) = try await URLSession.shared.data(from: url)
articles = try JSONDecoder().decode([Article].self, from: data)
} catch {
articles = []
}
}
}
}
I have a code, that should match 2 JSON files and connect all data in one struct. I'm pretty sure that It works just fine, but I have faced very strange problem. I want to make a picker:
import SwiftUI
struct CurrencyView: View {
#ObservedObject var api = CurrencyViewModel()
#State private var pickerSelection1 = 1
var body: some View {
Text("f")
Picker("", selection: $pickerSelection1) {
ForEach(0..<self.api.currencies.fullName.count) { // Error here
let currency = api.currencies.fullName[$0] // and here
Text(currency)
}
}
.id(UUID())
.labelsHidden()
.padding(.leading)
}
}
struct CurrencyView_Previews: PreviewProvider {
static var previews: some View {
CurrencyView()
}
}
It shows this error:
Value of type '[Currency]' has no member 'fullName'
I know I'm missing smth and feel stupid, because I can't understand why. Thanks for the reply!)
Adding the rest of the code:
// Model
import Foundation
struct CurrencyModel: Codable {
var results: [String:Double]
}
struct CurrencyNewModel: Codable {
var currencies: [String:String]
}
struct Currency: Decodable {
let currencyCode: String
let fullName: String
var price: Double
}
// View Model
import SwiftUI
class CurrencyViewModel: ObservableObject {
#Published var currencies: [Currency] = []
init() {
fetchNewData { [self] (currency) in
switch currency {
case .success(let names):
print("Success")
DispatchQueue.main.async {
self.currencies = names.currencies.map {
Currency(currencyCode: $0.key, fullName: $0.value, price: 0)
}
}
fetchData { result in
switch result {
case .success(let prices):
print("Success")
for (index, value) in currencies.enumerated() {
if let price = prices.results.first(where: { $0.key == value.currencyCode }) {
DispatchQueue.main.async {
currencies[index].price = price.value
}
}
}
case .failure(let error):
print(error)
}
}
case .failure(let error):
print("Error", error)
}
}
}
func fetchData(completion: #escaping (Result<CurrencyModel,Error>) -> ()) {
guard let url = URL(string: "https://api.fastforex.io/fetch-all?from=USD&api_key=7ffe65c2ef-926f01d9e8-r7eql2") else { return }
URLSession.shared.dataTask(with: url) { data, responce, error in
if let error = error {
completion(.failure(error))
return
}
guard let safeData = data else { return }
do {
let currency = try JSONDecoder().decode(CurrencyModel.self, from: safeData)
completion(.success(currency))
}
catch {
completion(.failure(error))
}
}
.resume()
}
func fetchNewData(completion: #escaping (Result<CurrencyNewModel,Error>) -> ()) {
guard let url = URL(string: "https://api.fastforex.io/currencies?api_key=7ffe65c2ef-926f01d9e8-r7eql2") else { return }
URLSession.shared.dataTask(with: url) { data, responce, error in
if let error = error {
completion(.failure(error))
return
}
guard let safeData = data else { return }
do {
let currency = try JSONDecoder().decode(CurrencyNewModel.self, from: safeData)
completion(.success(currency))
}
catch {
completion(.failure(error))
}
}
.resume()
}
}
P.S. If you want to see the API, check the links in fetchData and fetchNewData, It's a free trial, so doesn't matter
Your error says:
Value of type '[Currency]' has no member 'fullName'
So it seems that api.currencies is an array – the array itself has no member fullName, only one single element of it has.
try this:
ForEach(api.currencies, id:\.currencyCode) { currency in
Text(currency.fullName)
}
Here I want to be able to use the value returned from an array. It returns as a type from a struct. I'm unsure of how to use the value as an integer.
struct Item: Codable {
let data: [String : Datum]
}
struct Datum: Codable {
let value: Int
}
var array = Item(data: ["1" : Datum(value: 1),"2": Datum(value: 2), "3":Datum(value: 3)])
var keyArray = ["1", "2", "3"]
print(array.data[keyArray[0]]!)
// Prints Datum(value: 1)
print(array.data[keyArray[0]]! + 1)
//This produces an error "Cannot convert value of type 'Datum' to expected argument type 'Int'"
//Expected result should be 2
My use case is when I get returned a decoded JSON it normally comes back as a dictionary. I'm wanting to use the values returned with a key but I feel like I'm one step short.
Context
Full JSON Link
I'm going to retrieve values from this JSON. (Example from large JSON file)
{"data":{"2":{"high":179,"highTime":1628182107,"low":177,"lowTime":1628182102},"6":{"high":189987,"highTime":1628179815,"low":184107,"lowTime":1628182100},"8":{"high":190800,"highTime":1628181435,"low":188100,"lowTime":1628182095}
}}
The string in front refers to an item ID.
The struct that I came up to decode goes like this.
// MARK: - Single
struct Single: Codable {
let data: [String: Datum]
}
// MARK: - Datum
struct Datum: Codable {
let high, highTime: Int
let low, lowTime: Int?
}
From there I'm planning to iterate through the JSON response to retrieve the item prices I'd want.
#available(iOS 15.0, *)
struct ContentView: View {
#State var dataFromURL: Single = Single(data: [:])
var body: some View {
VStack {
Text("Hello, world!")
.padding()
}
.onAppear {
async {
try await decode()
}
}
}
func decode() async throws -> Single {
let decoder = JSONDecoder()
let urlString = "https://prices.runescape.wiki/api/v1/osrs/latest"
guard let url = URL(string: urlString) else { throw APIError.invalidURL }
let (data, response) = try await URLSession.shared.data(from: url)
guard let response = response as? HTTPURLResponse, response.statusCode == 200 else { throw APIError.invalidServerResponse }
guard let result = try? decoder.decode(Single.self, from: data) else { throw APIError.invalidData }
//We copy our result to an existing variable
dataFromURL = result
return result
}
}
enum APIError: Error {
case invalidURL
case invalidServerResponse
case invalidData
}
extension APIError: CustomStringConvertible {
public var description: String {
switch self {
case.invalidURL:
return "Bad URL"
case .invalidServerResponse:
return "The server did not return 200"
case .invalidData:
return "Their server returned bad data"
}
}
}
I haven't gotten further than grabbing the response from the URL. That is why once I start manipulating the data I'd like to use the response to find other things like what would a profit/loss with another item become. Which isn't the goal of this question at the moment.
The object model to parse that JSON would be:
struct Price: Decodable {
let high: Int?
let highTime: Date?
let low: Int?
let lowTime: Date?
}
struct ResponseObject: Decodable {
let prices: [String: Price]
enum CodingKeys: String, CodingKey {
case prices = "data"
}
}
(Note, the documentation says that either high or low might be missing, so we have to make them all optionals.)
Now, the id number is being passed as a string in the JSON/ResponseObject. But that is a number (look at mapping). So, I would remap that dictionary so that the key was an integer, e.g.
enum ApiError: Error {
case unknownError(Data?, URLResponse?)
}
func fetchLatestPrices(completion: #escaping (Result<[Int: Price], Error>) -> Void) {
let url = URL(string: "https://prices.runescape.wiki/api/v1/osrs/latest")!
let task = URLSession.shared.dataTask(with: url) { data, response, error in
guard
error == nil,
let responseData = data,
let httpResponse = response as? HTTPURLResponse,
200..<300 ~= httpResponse.statusCode
else {
completion(.failure(error ?? ApiError.unknownError(data, response)))
return
}
let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .secondsSince1970
do {
let responseObject = try decoder.decode(ResponseObject.self, from: responseData)
let keysAndValues = responseObject.prices.map { (Int($0.key)!, $0.value) }
let prices = Dictionary(uniqueKeysWithValues: keysAndValues)
completion(.success(prices))
} catch {
completion(.failure(error))
}
}
task.resume()
}
The code that converts that [String: Price] to a [Int: Price] is this:
let keysAndValues = responseObject.prices.map { (Int($0.key)!, $0.value) }
let prices = Dictionary(uniqueKeysWithValues: keysAndValues)
I must say that this is a questionable API design, to have keys returned as integers in one endpoint and as strings as another. But it is what it is. So, the above is how you handle that.
Anyway, now that you have a dictionary of prices, keyed by the id numbers, you can use that in your code, e.g.
var prices: [Int: Price] = [:]
var products: [Product] = []
let group = DispatchGroup()
group.enter()
fetchLatestPrices { result in
defer { group.leave() }
switch result {
case .failure(let error):
print(error)
case .success(let values):
prices = values
}
}
group.enter()
fetchProducts { result in
defer { group.leave() }
switch result {
case .failure(let error):
print(error)
case .success(let values):
products = values }
}
group.notify(queue: .main) {
for product in products {
print(product.name, prices[product.id] ?? "no price found")
}
}
Where
func fetchProducts(completion: #escaping (Result<[Product], Error>) -> Void) {
let url = URL(string: "https://prices.runescape.wiki/api/v1/osrs/mapping")!
let task = URLSession.shared.dataTask(with: url) { data, response, error in
guard
error == nil,
let responseData = data,
let httpResponse = response as? HTTPURLResponse,
200..<300 ~= httpResponse.statusCode
else {
completion(.failure(error ?? ApiError.unknownError(data, response)))
return
}
do {
let products = try JSONDecoder().decode([Product].self, from: responseData)
completion(.success(products))
} catch {
completion(.failure(error))
}
}
task.resume()
}
And
struct Product: Decodable {
let id: Int
let name: String
let examine: String
let members: Bool
let lowalch: Int?
let limit: Int?
let value: Int
let highalch: Int?
let icon: String
}
(As an aside, I do not know if some of these other properties should be optionals or not. I just used optionals where I empirically discovered that they are occasionally missing.)
I want to get Json from API, and use Codable protocol, but when I init published var, I get an error.
struct Search: Codable {
let result: [String]
}
class SearchViewModel: ObservableObject {
#Published var data = Search()
func loadData(search: String) {
var urlComps = URLComponents(string: getUrl)
let queryItems = [URLQueryItem(name: "result", value: search)]
urlComps!.queryItems = queryItems
let url = urlComps!.url!.absoluteString
guard let Url = URL(string: url) else { return }
URLSession.shared.dataTask(with: Url) { (data, res, err) in
do {
if let data = data {
let decoder = JSONDecoder()
let result = try decoder.decode(Search.self, from: data)
DispatchQueue.main.async {
self.data = result
}
} else {
print("there's no Data😭")
}
} catch (let error) {
print("Error!")
print(error.localizedDescription)
}
}.resume()
}
}
Change
#Published var data:Search?
I successfully fetched and decoded data from an API and now have access to all the data I need to be used in the algorithm I want to write in my App.
The issue is that I don't know how to access this data after I decoded it, I can print it immediately after it's decoded but I have no idea how to use it in another function or place in my app.
Here is my Playground:
import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true
enum MyError : Error {
case FoundNil(String)
}
struct Level: Codable {
let time: Double
let close: Double
let high: Double
let low: Double
let open: Double
}
struct Response: Codable {
let data: [Level]
private enum CodingKeys : String, CodingKey {
case data = "Data"
}
}
func fetchData(completion: #escaping (Response?, Error?) -> Void) {
let url = URL(string: "https://min-api.cryptocompare.com/data/histominute?fsym=BTC&tsym=USD&limit=60&aggregate=3&e=CCCAGG")!
let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
guard let data = data else { return }
do {
if let marketData = try? JSONDecoder().decode(Response.self, from: data) {
print(marketData.data[0].open)
print(marketData.data[1].open)
print("Average=", (marketData.data[0].open + marketData.data[1].open) / 2)
//completion(marketData, nil)
throw MyError.FoundNil("data")
}
} catch {
print(error)
}
}
task.resume()
}
fetchData() { items, error in
guard let items = items,
error == nil else {
print(error ?? "Unknown error")
return
}
print(items)
}
How can I use .data[0], .data[1], ..., somewhere else?
You data will be available in your fecthData() call. Probably what you want is your items variable, where you're printing it. But make sure to call the completion in your fetchData implementation.
WARNING: Untested code.
import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true
enum MyError: Error {
case FoundNil(String)
case DecodingData(Data)
}
struct Level: Codable {
let time: Double
let close: Double
let high: Double
let low: Double
let open: Double
}
struct Response: Codable {
let data: [Level]
private enum CodingKeys : String, CodingKey {
case data = "Data"
}
}
func fetchData(completion: #escaping (Response?, Error?) -> Void) {
let url = URL(string: "https://min-api.cryptocompare.com/data/histominute?fsym=BTC&tsym=USD&limit=60&aggregate=3&e=CCCAGG")!
let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
guard let data = data else {
completion(nil, MyError.FoundNil("data"))
}
do {
if let marketData = try? JSONDecoder().decode(Response.self, from: data) {
completion(marketData, nil)
} else {
completion(nil, MyError.DecodingData(data)) // work on this duplicated call
}
} catch {
completion(nil, MyError.DecodingData(data)) // work on this duplicated call
}
}
task.resume()
}
fetchData() { items, error in
if let error == error {
switch(error) {
case .foundNil(let whatsNil):
print("Something is nil: \(whatsNil)")
case .decodingData(let data):
print("Error decoding: \(data)")
}
} else {
if let items = items {
print(items.data[0].open)
print(items.data[1].open)
print("Average=", (items.data[0].open + items.data[1].open) / 2)
print(items)
} else {
print("No items to show!")
}
}
}
I don't understand what is your real issue, because you have written everything you need here, but as far I understand , to pass data
just uncomment this line completion(marketData, nil)
and in
fetchData() { items, error in
guard let items = items,
error == nil else {
print(error ?? "Unknown error")
return
}
print(items)
}
items is an object of your struct Response. You can pass this anywhere in your other class , by just creating an another variable like:
var items : Response!
for example :
class SomeOtherClass : NSObject{
var items : Response!
func printSomeData()
{
print(items.data[0].open)
print(items.data[1].open)
print("Average=", (items.data[0].open + items.data[1].open) / 2)
}
}
and in fetchData method write this:
fetchData() { items, error in
guard let items = items,
error == nil else {
print(error ?? "Unknown error")
return
}
let otherObject = SomeOtherClass()
otherObject.items = items
otherObject.printSomeData()
}