Reading countries names from JSON file problem - ios

Question

I am trying to load and parse countries names from json file using swift but I can't
This is file's format which I try to read: Countries JSON File
My code to do this task:
func getJsonFromUrl(){
let url = NSURL(string: COUNTRIES_URL)
URLSession.shared.dataTask(with: (url as URL?)!, completionHandler: {(data, response, error) -> Void in
if let jsonObj = try? JSONSerialization.jsonObject(with: data!, options: .allowFragments) as? NSDictionary {
if let countries_array = jsonObj!.value(forKey: "name") as? NSArray {
for country in countries_array {
if let countryDict = country as? NSDictionary {
if let name = countryDict.value(forKey: "name") {
self.countries_names.append((name as? String)!)
}
}
}
}
OperationQueue.main.addOperation ({
self.showNames()
})
}
}).resume()
}
But when I run it, it gives me an error in this line: if let countries_array = jsonObj!.value(forKey: "name") as? NSArray {
because of an unexpected nil.

Answer 1

The JSON starts with a bracket ([) therefore the root object is an array
Don't use NSURL, NSArray and NSDictionary and value(forKey in Swift.
And handle possible errors.
func getJsonFromUrl() {
let url = URL(string: COUNTRIES_URL)!
URLSession.shared.dataTask(with: url!, completionHandler: {(data, response, error) -> Void in
if let error = error { print(error); return }
do {
if let countriesArray = try JSONSerialization.jsonObject(with: data!) as? [[String:String]] {
for country in countriesArray {
self.countries_names.append(country["name"]!)
}
}
} catch { print(error) }
OperationQueue.main.addOperation ({
self.showNames()
})
}).resume()
}
Or much more convenient with Decodable
struct Country : Decodable {
let name : String
}
func getJsonFromUrl() {
let url = URL(string: COUNTRIES_URL)!
URLSession.shared.dataTask(with: url!, completionHandler: {(data, response, error) -> Void in
if let error = error { print(error); return }
do {
let countries = try JSONDecoder().decode([Country].self, from: data!)
self.countries_names = countries.map{$0.name}
} catch { print(error) }
OperationQueue.main.addOperation ({
self.showNames()
})
}).resume()
}

Answer 2

It's an array not dictionary you need
if let dat = data {
if let jsonObj = try? JSONSerialization.jsonObject(with: dat, options:[]) as? [[String:String]]{
jsonObj.forEach { print($0["name"]) }
}
or use Codable
let res = try? JSONDecoder().decode([[String:String]].self,from:data)
or with model
struct Root: Codable {
let name : String
}
let res = try? JSONDecoder().decode([Root].self,from:data)