Parsing RSS XML in WidgetView Extension of iOS 14

Question

I have an XMLParser set up in Swift in my app, and want to be able to within the widget extension, parse the RSS feed, and return that data in the widget. However, I'm having some issues getting the two Swift files to talk to each other. In the Parser, I have:

struct RSSItem {
    var title: String
    var description: String
    var link: String
    var pubDate: String
}

// download xml from the internet

class FeedParser: NSObject, XMLParserDelegate
{
    private var rssItems: [RSSItem] = []
    private var currentElement = ""
    private var currentTitle: String = ""
    private var currentDescription: String = ""
    private var currentPubDate: String = ""
    private var currentLink: String = ""
    
    private var parserCompletionHandler: (([RSSItem]) -> Void)?
    
    func parseFeed(url: String, completionHandler: (([RSSItem]) -> Void)?)
    {
        self.parserCompletionHandler = completionHandler
        
        let request = URLRequest(url: URL(string: url)!)
        let urlSession = URLSession.shared
        let task = urlSession.dataTask(with: request) { (data, response, error) in
            guard let data = data else {
                if let error = error {
                    print(error.localizedDescription)
                }
                
                return
            }
            
            /// parse our xml data
            let parser = XMLParser(data: data)
            parser.delegate = self
            parser.parse()
        }
        
        task.resume()
    }
    // MARK: - XML Parser Delegate

    func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String] = [:]) {
        if currentElement == "item" {
            currentTitle = ""
            currentDescription = ""
            currentPubDate = ""
            currentLink = ""
        }
    }
    func parser(_ parser: XMLParser, foundCharacters string: String) {
        switch currentElement {
        case "title": currentTitle += string
        case "description": currentDescription += string
        case "pubDate" : currentPubDate += string
        case "link" : currentLink += string
        default: break
        }
    }
    func parser(_ parser: XMLParser, didEndElement elementName: String, namespaceURI: String?, qualifiedName qName: String?) {
        if elementName == "item" {
            let rssItem = RSSItem(title: currentTitle, description: currentDescription, link: currentLink, pubDate: currentPubDate)
            self.rssItems.append(rssItem)
        }
    }
    func parserDidEndDocument(_ parser: XMLParser) {
        parserCompletionHandler?(rssItems)
    }
    
    func parser(_ parser: XMLParser, parseErrorOccurred parseError: Error) {
        print(parseError.localizedDescription)
    }
}

In the Widget, I have:

struct Provider: TimelineProvider {
    @State private var rssItems:[RSSItem]?
    let feedParser = FeedParser()
    func placeholder(in context: Context) -> SimpleEntry {
        SimpleEntry(date: Date(), title:"News", description: "Stuff happened", link: "Http://link", pubDate: "The day it posted")
    }

    func getSnapshot(in context: Context, completion: @escaping (SimpleEntry) -> ()) {
        let entry = SimpleEntry(date: Date(), title:"News", description: "Stuff happened", link: "Http://link", pubDate: "The day it posted")
        completion(entry)
    }

    func getTimeline(in context: Context, completion: @escaping (Timeline<Entry>) -> ()) {
        var entries: [SimpleEntry] = []
        feedParser.parseFeed(url: "") {(rssItems) in
            self.rssItems = rssItems
            let currentDate = Date()
            for hourOffset in 0 ..< 5 {
                let entryDate = Calendar.current.date(byAdding: .hour, value: hourOffset, to: currentDate)!
                let entry = SimpleEntry(date: entryDate, title:rssItems.title, description: rssItems.description, link: rssItems.link, pubDate: rssItems.pubDate)
                entries.append(entry)
            
        }
        // Generate a timeline consisting of five entries an hour apart, starting from the current date.
       
        }

        let timeline = Timeline(entries: entries, policy: .atEnd)
        completion(timeline)
    }
}

struct SimpleEntry: TimelineEntry {
    let date: Date
    let title: String
    let description: String
    let link: String
    let pubDate: String
}

However, in the TimelineProvider section, it tells me that rssItems has no member named title, description, pubDate, or link

Answer 1

You can't use @State variables outside SwiftUI views - which means you can't use them in a TimelineProvider.

You can do it with WidgetCenter.shared.reloadAllTimelines():

1. Update FeedParser to store parsed RSSItems and notify WidgetCenter when finished:

class FeedParser: NSObject, XMLParserDelegate {
    var rssItems: [RSSItem] = [] // make public, here you will store parsed RSSItems

    func parseFeed(url: String) { // remove `completionHandler` form the function signature
        ...
    }

    func parserDidEndDocument(_ parser: XMLParser) {
        // instead of calling `completionHandler` force reload the timeline
        WidgetCenter.shared.reloadAllTimelines()
    }
}

2. Get the first RSSItem from the FeedParser when creating the timeline and create an entry from it:

struct Provider: TimelineProvider {
    // no `@State` variables here

    let feedParser = FeedParser()

    ...

    func getTimeline(in context: Context, completion: @escaping (Timeline<Entry>) -> ()) {
        guard !feedParser.rssItems.isEmpty else { return }
        let entry = SimpleEntry(date: Date(), rssItem: feedParser.rssItems[0])
        
        let timeline = Timeline(entries: [entry], policy: .never)
        completion(timeline)
    }
}

3. For all this to work you need a way to know when the parseFeed function must be called again (to refresh items).

You may try to observe notifications for your feed and, when received, call:

feedParser.parseFeed(url: "some_feed")

(You need to use the same FeedParser instance for this, so it might be necessary to move the FeedParser out of the Provider)