NavigationView with Loading More in a List Crashes with Long Press only on iPad - ios

Question

I am creating a list that loads data when the user reaches the bottom of the list. I can crash the app when I load more elements and long-press an element within the list. The view is wrapped in a NavigationView and a NavigationLink. When the app crashes, you get EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0) with the thread 1 specialized saying "RandomAccessCollection<>.index(_:offsetBy:))". Looking into the EXC_BAD_INSTRUCTION I thought it could be force unwrapping, but I don't see anywhere in the code that could cause this issue.
The issue only occurs on an iPad and happens randomly. With WWDC being yesterday, I thought this would have been fixed, so we downloaded the beta for Xcode 12, and this error still occurs.
Here is the full code:
import UIKit
import SwiftUI
import Combine
struct ContentView: View {
var body: some View {
RepositoriesListContainer(viewModel: RepositoriesViewModel())
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
enum GithubAPI {
static let pageSize = 10
static func searchRepos(query: String, page: Int) -> AnyPublisher<[Repository], Error> {
let url = URL(string: "https://api.github.com/search/repositories?q=\(query)&sort=stars&per_page=\(Self.pageSize)&page=\(page)")!
return URLSession.shared
.dataTaskPublisher(for: url) // 1.
.tryMap { try JSONDecoder().decode(GithubSearchResult<Repository>.self, from: $0.data).items } // 2.
.receive(on: DispatchQueue.main) // 3.
.eraseToAnyPublisher()
}
}
struct GithubSearchResult<T: Codable>: Codable {
let items: [T]
}
struct Repository: Codable, Identifiable, Equatable {
let id: Int
let name: String
let description: String?
let stargazers_count: Int
}
class RepositoriesViewModel: ObservableObject {
#Published private(set) var state = State()
private var subscriptions = Set<AnyCancellable>()
// 2.
func fetchNextPageIfPossible() {
guard state.canLoadNextPage else { return }
GithubAPI.searchRepos(query: "swift", page: state.page)
.sink(receiveCompletion: onReceive,
receiveValue: onReceive)
.store(in: &subscriptions)
}
private func onReceive(_ completion: Subscribers.Completion<Error>) {
switch completion {
case .finished:
break
case .failure:
state.canLoadNextPage = false
}
}
private func onReceive(_ batch: [Repository]) {
state.repos += batch
state.page += 1
state.canLoadNextPage = batch.count == GithubAPI.pageSize
}
// 3.
struct State {
var repos: [Repository] = []
var page: Int = 1
var canLoadNextPage = true
}
}
struct RepositoriesListContainer: View {
#ObservedObject var viewModel: RepositoriesViewModel
var body: some View {
RepositoriesList(
repos: viewModel.state.repos,
isLoading: viewModel.state.canLoadNextPage,
onScrolledAtBottom: viewModel.fetchNextPageIfPossible
)
.onAppear(perform: viewModel.fetchNextPageIfPossible)
}
}
struct RepositoriesList: View {
// 1.
let repos: [Repository]
let isLoading: Bool
let onScrolledAtBottom: () -> Void // 2.
var body: some View {
NavigationView {
List {
reposList
if isLoading {
loadingIndicator
}
}
}
// .OnlyStackNavigationView()
}
private var reposList: some View {
ForEach(repos) { repo in
// 1.
RepositoryRow(repo: repo).onAppear {
// 2.
if self.repos.last == repo {
self.onScrolledAtBottom()
}
}
.onTapGesture {
print("TAP")
}
.onLongPressGesture {
print("LONG PRESS")
}
}
}
private var loadingIndicator: some View {
Spinner(style: .medium)
.frame(idealWidth: .infinity, maxWidth: .infinity, alignment: .center)
}
}
struct RepositoryRow: View {
let repo: Repository
var body: some View {
NavigationLink(destination: LandmarkDetail()){VStack {
Text(repo.name).font(.title)
Text("⭐️ \(repo.stargazers_count)")
repo.description.map(Text.init)?.font(.body)
}}
}
}
struct Spinner: UIViewRepresentable {
let style: UIActivityIndicatorView.Style
func makeUIView(context: Context) -> UIActivityIndicatorView {
let spinner = UIActivityIndicatorView(style: style)
spinner.hidesWhenStopped = true
spinner.startAnimating()
return spinner
}
func updateUIView(_ uiView: UIActivityIndicatorView, context: Context) {}
}
struct LandmarkDetail: View {
var body: some View {
VStack {
VStack(alignment: .leading) {
Text("Turtle Rock")
.font(.title)
HStack(alignment: .top) {
Text("Joshua Tree National Park")
.font(.subheadline)
Spacer()
Text("California")
.font(.subheadline)
}
}
.padding()
Spacer()
}
}
}