Display fetched data in SwiftUI

Question

Created Nov ’22

Replies 1

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Hello, I want to fetch json data from an api and then display it in a view. It is showing me an error ("Missing return in global function expected to return 'Response'") in the end of the function. How can I return the fetched data and where should I put the return statement?

private func getData(from url: String) -> Response {
    let task = URLSession.shared.dataTask(with: URL(string: url)!, completionHandler: {
        data, response, error in

        guard let data = data, error == nil else {
            print("Something went wrong")
            return
        }
        
        var result: Response?

        do {
            result = try JSONDecoder().decode(Response.self, from: data)
        }

        catch {
            print("failed to convert \(error)")
        }

        guard let json = result else {
            return
        }

        print(json)

    })

    task.resume()
}

I call the function this way:

struct ShowData: View {
    @State var results: Response
    var body: some View {
        Text("Hello world").onAppear {
           results = getData(from: url)
        }
    }
}

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Answer 1

BabyJ OP

Nov ’22

Accepted Answer

You're kind of mixing up two approaches here: completion handlers and return values, like seen with async/await. Since your data fetch is using a completion handler, you can follow this route and add a completion closure parameter to the getData function which can then be called when you get the data.

Here's an example of what this would look like:

private func getData(from url: String, completion: @escaping (Response) -> Void) {
    let task = URLSession.shared.dataTask(with: URL(string: url)!) { data, response, error in
        ...

        completion(json)
    }

    task.resume()
}


// in SwiftUI View
.onAppear {
    getData(from: url) { results = $0 }
}

1