Unexpectedly found nil while unwrapping an - Optional Value

Question

I have the following implementation; however, I am getting the following error.

Thread 5: Fatal error: Unexpectedly found nil while unwrapping an Optional value

struct StoreProducts: Decodable {
  let totalProducts: Int?
  let pageNumber: Int?
}

var products: StoreProducts!

override func viewDidLoad() {
    super.viewDidLoad()

    fetchProducts(completion: { success in
        print(self.products as Any)
        self.products = products
        self.productTableView.reloadData()
    })
}

func fetchProducts(completion: @escaping ((Any) -> Void)) {
    let jsonUrlString = "https://mobile-server.com/products/1/20"
    guard let url = URL(string: jsonUrlString) else { return  }

    // Note: Swift 4 JSONCoder()
    URLSession.shared.dataTask(with: url) { (data, response, err) in
        guard let data = data else { return }
        do {
            // getting error here
            self.products = try JSONDecoder().decode(StoreProducts.self, from: data)
            //check response status 200 OK
            if pageProducts.statusCode != 200
            {
                print("Connection issue, please try again later")
            }
            else{
                completion(self.products as Any)
            }
        }
        //check error
        catch let jsonErr {
            print("Error serializing json:", jsonErr)
        }
    }.resume()
}

Why do you have your products as a global variable instead of passing them as part of the completion handler? — Andy Ibanez, Jun 19 '18 at 02:37
@AndyIbanez, I am newbee to swift. I would like to learn what is the right way of doing it. — casillas, Jun 19 '18 at 02:39
So I see many problems with your code, but the actual cause for the nil unwrapping is not clear yet. Try to post an MCVE that people can build and run to help you better. — Andy Ibanez, Jun 19 '18 at 02:56
It would be great, if you just describe the issues that you see. — casillas, Jun 19 '18 at 03:12

Christian Abella · Accepted Answer · 2018-06-19T03:51:18.153

2

I tried your code and not sure where you declare the pageProducts but you need to check the response variable instead and cast it to HTTPURLReponse if you want to check the statusCode of the HTTP call.

fetchProducts(completion: { success in
  if let products = success as? StoreProducts
  {
     print(products.totalProducts!)
     print(products.pageNumber!)
   }
})


func fetchProducts(completion: @escaping ((AnyObject) -> Void)) {
    let jsonUrlString = "https://mobile-tha-server.appspot.com/walmartproducts/1/20"
    guard let url = URL(string: jsonUrlString) else { return  }

    // Note: Swift 4 JSONCoder()
    URLSession.shared.dataTask(with: url)
    { (data, response, err) in
      guard let data = data else { return }
      do {
        // getting error here
        self.products = try JSONDecoder().decode(StoreProducts.self, from: data)
        //check response status 200 OK
        if let httpResponse = response as? HTTPURLResponse, httpResponse.statusCode != 200 {
          print("Connection issue, please try again later")
        }
        else{
          completion(self.products as AnyObject)
        }
      }
        //check error
      catch let jsonErr {
        print("Error serializing json:", jsonErr)
      }
      }.resume()
  }

edited Jun 19 '18 at 03:51

answered Jun 19 '18 at 02:54

Christian Abella

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Unfortunately, it did not help. – casillas Jun 19 '18 at 03:12
do you have a valid URL that we can test? or can you post your other code? – Christian Abella Jun 19 '18 at 03:17
let jsonUrlString = "https://mobile-tha-server.appspot.com/walmartproducts/1/20" – casillas Jun 19 '18 at 03:31
I edited my answer. I got a response of 224 products and 1 as pageNumber – Christian Abella Jun 19 '18 at 03:44
please copy and paste my code to your environment and see if it works. It is working on my side. – Christian Abella Jun 19 '18 at 03:45
Could you please include also URLSession part into your code? – casillas Jun 19 '18 at 03:49
updated my answer – Christian Abella Jun 19 '18 at 03:51
When I reloadTableView after data is retrived, then I am getting the following error .This application is modifying the autolayout engine from a background thread after the engine was accessed from the main thread. This can lead to engine corruption and weird crashes. – casillas Jun 19 '18 at 03:53
1

you need to enclosed your UI calls inside the main queue: DispatchQueue.main.async { // ui function calls } – Christian Abella Jun 19 '18 at 04:04

Unexpectedly found nil while unwrapping an - Optional Value

1 Answers1