How display a JSON in the UI in swift

Question

I try to adapt my Android application on iPhone, but when I ask my server to get a JSON object I have a fatal error:

fatal error: unexpectedly found nil while unwrapping an Optional value

I think I have a bad initialization of my text field in my story board or something else but I can't find my error.

The print(jsonResult) gives me the good JSON but after I have my fatal error that appear.

import UIKit

class ViewController: UIViewController {



@IBOutlet weak var labelCategory: UILabel!
@IBOutlet weak var imageViewOneTrash: UIImageView!
@IBOutlet weak var textFieldCoordinate: UITextField!
@IBOutlet weak var textFieldAddress: UITextField!
@IBOutlet weak var buttonShare: UIButton!
@IBOutlet weak var buttonCoppy: UIButton!
@IBOutlet weak var buttonDelete: UIButton!
@IBOutlet weak var buttonMaps: UIButton!
@IBOutlet weak var addressTxtFld: UITextField!

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    // 1
    let urlAsString = "http://www.website.sample"
    let url = NSURL(string: urlAsString)!
    let urlSession = NSURLSession.sharedSession()

    //2
    let jsonQuery = urlSession.dataTaskWithURL(url, completionHandler: { data, response, error -> Void in
        if (error != nil) {
            print(error!.localizedDescription)
        }

        // 3
        do{
            if let jsonResult = try NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.MutableContainers) as? [String:AnyObject] {

                print(jsonResult)
                // 4
                let jsonAddress: String! = jsonResult["trash_temp_address"] as! String

                dispatch_async(dispatch_get_main_queue(), {
                    self.addressTxtFld.text = jsonAddress
                })
            }

        }catch let error as NSError {
            print(error.localizedDescription)
        }

    })
    // 5
    jsonQuery.resume()

}

  override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

The result of the print(jsonResult) is:

["result": <__NSArrayM 0x15d62770>(
{
    "cat_name" = Mobilier;
    "country_name" = France;
    "town_name" = Toulon;
    "town_postal_code" = 83200;
    "trash_temp_address" = "278-338 Chemin du Jonquet";
    "trash_temp_date_time" = "2016-05-22 17:49:14";
    "trash_temp_fk_category" = 2;
    "trash_temp_id" = 99;
    "trash_temp_img" = "/pics/IMG_20160622_174846.jpg.png";
    "trash_temp_latitude" = "43.1395197";
    "trash_temp_longitude" = "5.9106404";
}
)
]

where do you get this error, which line?

rounak
– rounak

2016-06-22 19:52:35 +00:00
Commented Jun 22, 2016 at 19:52 — rounak
– rounak, Commented Jun 22, 2016 at 19:52
I don"t have a line number, I put the json in my question

Fred37b
– Fred37b

2016-06-22 19:59:43 +00:00
Commented Jun 22, 2016 at 19:59 — Fred37b
– Fred37b, Commented Jun 22, 2016 at 19:59

vadian · Accepted Answer · 2016-06-22 20:03:48Z

3

The root object is a dictionary with one key result.
The value for key result is an array of dictionaries

This gets the value for key trash_temp_address

if let jsonRootObject = try NSJSONSerialization.JSONObjectWithData(data!, options: []) as? [String:AnyObject] { // mutable containers are not needed

    print(jsonRootObject)
    if let jsonResult = jsonRootObject["result"] as? [[String:String]],
       jsonAddress = jsonResult[0]["trash_temp_address"] {    
          dispatch_async(dispatch_get_main_queue()) {
             self.addressTxtFld.text = jsonAddress
          }
    }
    ...

answered Jun 22, 2016 at 20:03

vadian

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Comments

Lou Franco · Accepted Answer · 2016-06-22 20:04:36Z

0

Your print(jsonResult)

shows an object with a result key and an array with one object that has your "trash_temp_address"

You access that something like this:

let result = jsonResult["result"] as! [AnyObject]
let resultObj = result[0] as! [String: AnyObject]
let jsonAddress = resultObj["trash_temp_address"] as! String

(you might need to correct this, as I am not trying it in Xcode)

answered Jun 22, 2016 at 20:04

Lou Franco

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Comments

Alexey Matjuk · Accepted Answer · 2016-06-22 20:10:38Z

0

First possible crash could happen here:

let jsonAddress: String! = jsonResult["trash_temp_address"] as! String

Try to avoid implicit unwrapping of optionals. Moreover text property is already optional. So and we can write:

let jsonAddress = jsonResult["trash_temp_address"] as? String

Next crash could happen here:

self.addressTxtFld.text = jsonAddress

if addressTxtFld outlet is not connected in storyboard or nib file. To fix it write this

self.addressTxtFld?.text = jsonAddress

P.S. These advices fixes possible crashes. But not wrong logic. With new information (JSON structure) it is obvious logic is wrong. @vadian gave you an example of correct parsing logic.

edited Jun 22, 2016 at 20:10

answered Jun 22, 2016 at 20:02

Alexey Matjuk

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2 Comments

Fred37b Over a year ago

the "let jsonAddress = jsonResult["trash_temp_address"] as? String" delete the fatal error, but when I do print(jsonAddress) it print nil

Alexey Matjuk Over a year ago

yes. Because jsonResult is wrapping dictionary. I updated my answer and suggesting to look at @vadian answer

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