I think I need to use Combine, but I'm not yet sure how...

Question

Created Jul ’20

Replies 3

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Participants 2

I have a row view that shows the details of a podcast object.
It includes a Subscribe/Unsubscribe button (displayed text depends on whether the user is currently subscribed.)
(podcast uses a computed property to express isSubscribed)
This means when a user taps the button, the Subscribe/Unsubscribe text should change, but it does not.
I'm pretty sure I need to use combine for the podcast model object to publish an event, but I don't yet know what this code looks like.
Any chance somebody could let me know how I need to extend the code below to do this?
thanks,
Mike

class SubscriptionsManager {
var subscriptions: [Podcast] = []
static let shared = SubscriptionsManager()
func toggleSubscription(podcast: Podcast) {

}
func isSubscribed(podcast: Podcast) -> Bool {
let result = subscriptions.first{ $0.id == podcast.id }
return result != nil
}
}

class Podcast: Codable {
let title: String
let id: String
var isSubscribed: Bool {
return SubscriptionsManager.shared.isSubscribed(podcast: self)
}
func toggleSubscription() {
SubscriptionsManager.shared.toggleSubscription(podcast: self)
}
}

struct PodcastRowView: View {
@State var podcast: Podcast
var buttonText: String {
return podcast.isSubscribed ? "Unsubscribe" : "Subscribe"
}
var body: some View {
HStack {
Text(podcast.title)
Button(action: {
self.podcast.toggleSubscription()
}) {
Text(self.buttonText)
}
}
}
}

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Answer 1

mikeTheDad OP

Jul ’20

Looks like I figured it out:

Podcast needs to conform to ObservableObject
add the following line to Podcast's toggleSubscription function

Code Block 	objectWillChange.send()

3. in PodcastRowView replace @State with @ObservableObject

0

Answer 2

OOPer OP

Jul ’20

An easy way to work with Combine in SwiftUI is using @Published var.

Code Block class SubscriptionsManager: ObservableObject {
		@Published var subscriptions: [Podcast] = []
		//...
}
struct PodcastRowView: View {
		@ObservedObject var subscriptionsManager = SubscriptionsManager.shared
		//...
}

The changes on @Published vars inside @ObservedObject will trigger the UI update with internally using Combine.

0

Answer 3

mikeTheDad OP

Jul ’20

thanks @OOPer I like this alternative approach

0