SwiftUI combine nil data - swiftui

Question

I have created a class to perform a network request and parse the data using Combine. I'm not entirely certain the code is correct, but it's working as of now (still learning the basics of Swift and basic networking tasks). My Widget has the correct data and is works until the data becomes nil. Unsure how to check if the data from my first publisher in my SwiftUI View is nil, the data seems to be valid even when there's no games showing.
My SwiftUI View
struct SimpleEntry: TimelineEntry {
let date: Date
public var model: CombineData?
let configuration: ConfigurationIntent
}
struct Some_WidgetEntryView : View {
var entry: Provider.Entry
#Environment(\.widgetFamily) var widgetFamily
var body: some View {
VStack (spacing: 0){
if entry.model?.schedule?.dates.first?.games == nil {
Text("No games Scheduled")
} else {
Text("Game is scheduled")
}
}
}
}
Combine
import Foundation
import WidgetKit
import Combine
// MARK: - Combine Attempt
class CombineData {
var schedule: Schedule?
var live: Live?
private var cancellables = Set<AnyCancellable>()
func fetchSchedule(_ teamID: Int, _ completion: #escaping (Live) -> Void) {
let url = URL(string: "https://statsapi.web.nhl.com/api/v1/schedule?teamId=\(teamID)")!
let publisher = URLSession.shared.dataTaskPublisher(for: url)
.map(\.data)
.decode(type: Schedule.self, decoder: JSONDecoder())
//.catch { _ in Empty<Schedule, Error>() }
//.replaceError(with: Schedule(dates: []))
let publisher2 = publisher
.flatMap {
return self.fetchLiveFeed($0.dates.first?.games.first?.link ?? "")
}
Publishers.Zip(publisher, publisher2)
.receive(on: DispatchQueue.main)
.sink(receiveCompletion: {_ in
}, receiveValue: { schedule, live in
self.schedule = schedule
self.live = live
completion(self.live!)
WidgetCenter.shared.reloadTimelines(ofKind: "NHL_Widget")
}).store(in: &cancellables)
}
func fetchLiveFeed(_ link: String) -> AnyPublisher<Live, Error /*Never if .catch error */> {
let url = URL(string: "https://statsapi.web.nhl.com\(link)")!
return URLSession.shared.dataTaskPublisher(for: url)
.map(\.data)
.decode(type: Live.self, decoder: JSONDecoder())
//.catch { _ in Empty<Live, Never>() }
.eraseToAnyPublisher()
}
}

Answer 1

Like I said in the comments, it's likely that the decode(type: Live.self, decoder: JSONDecoder()) returns an error because the URL that you're fetching from when link is nil doesn't return anything that can be decoded as Live.self.
So you need to handle that case somehow. For example, you can handle this by making the Live variable an optional, and returning nil when link is empty (or nil).
This is just to set you in the right direction - you'll need to work out the exact code yourself.
let publisher2 = publisher1
.flatMap {
self.fetchLiveFeed($0.dates.first?.games.first?.link ?? "")
.map { $0 as Live? } // convert to an optional
.replaceError(with: nil)
}
Then in the sink, handle the nil:
.sink(receiveCompletion: {_ in }, receiveValue:
{ schedule, live in
if let live = live {
// normal treatment
self.schedule = schedule
self.live = live
//.. etc
} else {
// set a placeholder
}
})

Answer 2

SwiftUI and WidgetKit work differently. I needed to fetch data in getTimeline for my IntentTimelineProvider then add a completion handler for my TimelineEntry. Heavily modified my Combine data model. All credit goes to #EmilioPelaez for pointing me in the right direction, answer here.