Api Service Function Can Not Fetch Data At First Trial SwiftUI - json

Question

This API function of mine called fetchAuthorArticles can not fetch JSON data at the first tap. If I close the sheet and tap it once more it does fetch JSON and fills SelectedAuthorView screen accordingly. What might be the reason?
class AuthorService: ObservableObject {
#Published var authorArticles = AuthorList(author: Author(author_id: 0, articles: 0, newspaper_image: "", author_name: "", author_image: "", newspaper: ""), articles: [])
func fetchAuthorArticles(authorID: Int){
isLoadingPage = true
if let selectedAuthorUrl = URL(string:"http://author/article/list/\(authorID)/") {
let session = URLSession(configuration: .default)
var request = URLRequest(url: selectedAuthorUrl)
request.httpMethod = "GET"
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.addValue("application/json", forHTTPHeaderField: "Accept")
let task = session.dataTask(with: request as URLRequest) { (data, response, error) in
print(data)
print(response)
print(error)
if error == nil {
let decoder = JSONDecoder()
if let safeData = data {
do {
let results = try decoder.decode(AuthorArticleList.self, from: safeData)
DispatchQueue.main.async {
self.authorArticles = results
self.isLoadingPage = false
}
} catch {
print(error)
}
}
}
}
task.resume()
}
}
}
AuthorArticleList Model
struct AuthorArticleList:Decodable {
var author: Author
var articles: [Articles]
}
struct Author: Decodable, Identifiable {
var id: Int {
return author_id
}
var author_id: Int
var articles: Int
var newspaper_image: String
var author_name: String
var author_image: String
var newspaper: String
}
struct Articles: Decodable, Identifiable {
var id: Int {
return article_id
}
var article_id: Int
var title: String
var url: String
var abstract: String
var article_date: String
}
SelectedAuthorView
struct SelectedAuthorView: View {
#Binding var selectedAuthor: AuthorPost
#ObservedObject var service = AuthorService()
var cellNumber: Int = 0
let columns: [GridItem] = Array(repeating: GridItem(.flexible(), spacing: 0), count: 2)
var body: some View {
ScrollView(.vertical, showsIndicators: true) {
LazyVGrid(columns: columns, spacing: 0) {
ForEach(Array(service.authorArticles.articles.enumerated()), id: \.1.id) {i, post in
AuthorArticleListItem(articlePost: post, cellNumber: i)
}
.background(Color(.white))
if service.isLoadingPage {
ProgressView()
.padding()
.offset(x: UIScreen.main.bounds.width / 4)
}
}
.onAppear {
self.service.fetchAuthorArticles(authorID: selectedAuthor.author_id)
}