SWIFT decodable data transfer

Question

I have a usernameTextField in the viewController where I enter a username and a button searchTapped with the following code:

@IBAction func searchTapped(_ sender: UIButton) {
        guard let username = usernameTextField.text, username != "" else {
            displayWarningLabel(withText: "Information is incorrect")
            return
        }

        guard let gitUrl = URL(string: "https://api.github.com/users/\(username)/gists") else { return }
        URLSession.shared.dataTask(with: gitUrl) { (data, response, error) in

            guard let data = data else { return }
            guard error == nil else { return }
            do {
                let gitData = try JSONDecoder().decode([Gists].self, from: data)
                DispatchQueue.main.async {
                    self.gists = gitData
                }
            } catch let error {
                print(error)
            }
            }.resume()

        performSegue(withIdentifier: "GistsSegue", sender: nil)
    }

after I get the data from json I want to save the data into an array gists outside of this method, but this does not happen.

 var gists = [Gists]()

What could be the problem?

Just in case, this is my model for parsing json:

struct Gists: Codable {
    var description: String?
    var files: [String: DetailGist]
}

struct DetailGist: Codable {
    var filename: String?
    var raw_url: String?
}

Answer 1

self.gists = gitData is being called but it is called long after you call performSegue . This is the nature of asynchronous data access.

Simply move your performSegue call to be just after you set self.gists .

DispatchQueue.main.async {
    self.gists = gitData
    performSegue(withIdentifier: "GistsSegue", sender: nil)
}