SwiftUI - Navigate to view after retrieving data

Question

So I'm retrieving data from FireStore. I'm retrieving the data successfully. When I tap my search button the first time the data is being downloaded and the new view is pushed. As a result, I get a blank view. But when I go back, hit search again, sure enough I can see my data being presented.

How can I make sure I first have the data I'm searching for THEN navigate to the new view? I've used @State variables etc. But nothing seems to be working. I am using the MVVM approach.

My ViewModel:

class SearchPostsViewModel: ObservableObject { var post: [PostModel] = [] @State var searchCompleted: Bool = false func searchPosts(completed: @escaping() -> Void, onError: @escaping(_ errorMessage: String) -> Void) { isLoading = true API.Post.searchHousesForSale(propertyStatus: propertyStatus, propertyType: propertyType, location: location, noOfBathrooms: noOfBathroomsValue, noOfBedrooms: noOfBedroomsValue, price: Int(price!)) { (post) in self.post = post print(self.post.count) self.isLoading = false self.searchCompleted.toggle() } } }

The code that does work, but with the bug:

 NavigationLink(destination: FilterSearchResults(searchViewModel: self.searchPostsViewModel) .onAppear(perform: { DispatchQueue.main.async { self.createUserRequest() } }) ) { Text("Search").modifier(UploadButtonModifier()) }

Some specifics would be great! See stackoverflow.com/help/how-to-ask for the rules. — lorem ipsum
– lorem ipsum, Commented Aug 16, 2020 at 23:32

Asperi · Accepted Answer · 2020-08-17 03:56:13Z

Try with the following modified view model

class SearchPostsViewModel: ObservableObject { @Published var post: [PostModel] = [] // << make both published @Published var searchCompleted: Bool = false func searchPosts(completed: @escaping() -> Void, onError: @escaping(_ errorMessage: String) -> Void) { isLoading = true API.Post.searchHousesForSale(propertyStatus: propertyStatus, propertyType: propertyType, location: location, noOfBathrooms: noOfBathroomsValue, noOfBedrooms: noOfBedroomsValue, price: Int(price!)) { (post) in DispatchQueue.main.async { self.post = post // << update on main queue print(self.post.count) self.isLoading = false self.searchCompleted.toggle() } } } }

Yes, I've finally sorted. I needed to use the isActive parameter when using NavigationLink. And toggle the bool value in the completion handler.

lorem ipsum · Accepted Answer · 2020-08-16 23:43:26Z

You should look at the Apple documentation for @State and ObservableObject

https://developer.apple.com/documentation/combine/observableobject

https://developer.apple.com/documentation/swiftui/state

Your issue is with using an @State in a non-UI class/View.

It might help if you start with the Apple SwiftUI tutorials. So you understand the differences in with the wrappers and learn how it all connects.

https://developer.apple.com/tutorials/swiftui

Also, when you post questions make sure your code can be copied and pasted onto Xcode as-is so people can test it. You will get better feedback if other developers can see what is actually happening. As you progress it won't be as easy to see issues.

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