SwiftUI global var and func at launch

Question

I have this func that parses a json. Then I use the data for that to populate a bunch of UI slot. The problem is it's a big json (if 10.1MB is big) and it takes 5-8 seconds to load. At app launch that's no big deal, but right now it' reprising that data every time.

Right now I just have this mode were each struct view starts with:

var results = [ScryfallCard]()

.onApear {
    results = func()
}

func() -> [ScryfallCard]

I can't find for the life of me find out how to make a global variable, assign it the var globleResults = func() so my app loads all that data upfront and doesn't take 5 second to load each view.

Answer 1

In order for your view to update the results, you need to make turn your results results into @State var results: [ScryfallCard] = []

Then with your function that deals with the JSON, no matter how long it takes to process, it should update the view once the results = func() is finished.

Avoid using global variables and aim for creating different components to encapsulate the variables.

You would have something like this

class NetworkRequester: ObservableObject {

    @Published var results: [String] = []

    var cancellable: AnyCancellable?

    func getResults() {
        cancellable = URLSession.shared.dataTaskPublisher(for: URL(fileURLWithPath: "path-to-JSON")!)
            .map({ $0.data })
            .decode(type: [ScryfallCard].self, decoder: JSONDecoder())
            .sink(receiveCompletion: { result in
                switch result {
                    case .failure(let error):
                    print(error)
                    case .finished:
                    break
                }
            }) { newResults in
                self.results = newResults
        }
    }
}

The link suggested in the comment is a useful resource to learn more about how to deal with rendering data.