How to insert JSON array model in Swift? - json

Question

I have JSON like this but with more data:
[
{
"name": "Place 1",
"avatar": "https://sometext.it/image=1",
"id": "1",
"lng": 10.01,
"lat": 15.02
},
{
"name": "Place 2",
"avatar": "https://sometext.it/image=2",
"id": "2",
"lng": 15.02,
"lat": 15.03
}
]
I get JSON from URL and I want to insert them to array of places. I have class:
class Place {
var Avatar = ""
var Id = 0
var Lat = 0.0
var Lng = 0.0
var Name = ""
required init(avatar: String, id: Int, lat: Double, lng: Double, name: String) {
self.Avatar = avatar
self.Id = id
self.Lat = lat
self.Lng = lng
self.Name = name
}
}
And i create an Array:
var places: [Place] = []
I serialize JSON like this:
func parsingJson() {
guard let url = URL(string: "https://somelink.com") else {
return
}
let session = URLSession.shared
session.dataTask(with: url) { (data, response, error) in
if let response = response {
print(response)
}
if let data = data {
print(data)
do {
let json = try JSONSerialization.jsonObject(with: data, options: [])
for result in json as! [[String:Any]] {
let avatar = result["avatar"] as! String
let id = result["id"] as! Int
let lat = result["lat"] as! Double
let lng = result["lng"] as! Double
let name = result["name"] as! String
let place = Place(avatar: avatar, id: id, lat: lat, lng: lng, name: name)
self.places.append(place)
print(result)
}
}catch {
print("JSON Error")
}
}
}.resume()
}
but that doesn't work, I have error like this: http://obrazki.elektroda.pl/9267167800_1497627255.png
I know that I have nil but I don't know why :( When I print the JSON when I'm serialising I see it on console.

Answer 1

The first, you are trying to get ID as an INT, when your JSON Object is showing that it's a string.. So you would need to do:
var id = Int()
if let someID = result["id"] as? String {
id = Int(someId)
} else {
print("ID failed as String")
}
However, i'd also recommend using a guard statement before your for loop:
guard let json = try JSONSerialization.jsonObject(with: data, options: []) as? [[String:Any]] else {
print("Invalid json object type")
return
}
for result in json {
///your code.
}
you at least try to unwrap the variable, and get some Int instance to pass along
But obviously, the simpler solution would be to save the id field in your JSON to the type you would want on your front-end.. in this case a Number.
While it might not look as clean as your code, use unwraping methods like guards, and if-else logics as much as possible, and create failed unwrap fallbacks as much as possible as early on in your project. It helps in debugging down the line and creates a good base when your project becomes large enough.
Check up on Apple's guide and this here for some good starting points.
Late update, but re-reading on all this landed me on this neat article by Apple:
https://developer.apple.com/swift/blog/?id=37

Answer 2

You haven't nil, read error - Could not cast value of type NSTaggedPointerString to NSNumber This means that your id is String and you are casting it to Int so replace
let id = result["id"] as! Int
to
let id = result["id"] as! String