Why URLSession.DataTask.shared is not working properly? - ios

Question

I need to fetch some quizzes for my application from the server. Unfortunately, it seems that URLSession.DataTask.shared is not working. How do I fix the problem?
This is for Swift 4.
import Foundation
import UIKit
class QuizService {
let baseUrl = "https://iosquiz.herokuapp.com/api/quizzes"
func fetchQuizzes(completion: #escaping (([Quiz]?) -> Void)) -> Void {
if let url = URL(string: baseUrl) {
let request = URLRequest(url: url)
let dataTask = URLSession.shared.dataTask(with: request) { (data, response, error) in
if let data = data {
do {
let json = try JSONSerialization.jsonObject(with: data, options: [])
if let resultsList = json as? [String: Any], let results = resultsList["quizzes"] as? [[String: Any]] {
let quizzes = results.map({ json -> Quiz? in
print(json)
if
let title = json["title"] as? String,
let id = json["id"] as? Int,
let level = json["level"] as? Int,
let description = json["description"] as? String,
let category = json["category"] as? String,
let questions = json["questions"] as? [String: Any],
let imageUrl = json["image"] as? String {
let quiz=Quiz(id:id,title:title,descript:description,category:category,level:level,imageUrl:imageUrl,questions:questions)
return quiz
} else {
return nil
}
}).filter { $0 != nil } .map { $0! }
completion(quizzes)
} else {
completion(nil)
}
} catch {
completion(nil)
}
} else {
completion(nil)
}
}
dataTask.resume()
} else {
completion(nil)
}
}
}
My error is that field of quizzes are null, so my code is not working in my view controller.

Answer 1

I took a look at the response here https://iosquiz.herokuapp.com/api/quizzes.
The "questions" should be array of dictionaries instead of dictionary.
so it should works if you replace this line
let questions = json["questions"] as? [String: Any]
with this line
let questions = json["questions"] as? [[String: Any]]
BTW, I prefer to extract the logic of parsing json into another method to keep fetchQuizzes method simple.
Hope this helps!