Convert Json string to Json object in Swift 4

Question

I try to convert JSON string to a JSON object but after JSONSerialization the output is nil in JSON.

Response String:

[{\"form_id\":3465,\"canonical_name\":\"df_SAWERQ\",\"form_name\":\"Activity 4 with Images\",\"form_desc\":null}]

I try to convert this string with my code below:

let jsonString = response.result.value
let data: Data? = jsonString?.data(using: .utf8)
let json = (try? JSONSerialization.jsonObject(with: data, options: [])) as? [String:AnyObject]
 print(json ?? "Empty Data")

did you added the alamofire pod. https://www.google.com/search?ei=968KWufnFcvWvgS7rKW4BA&q=alamofire+swift+4&oq=alamofire&gs_l=psy-ab.1.2.0i71k1l4.0.0.0.19859.0.0.0.0.0.0.0.0..0.0....0...1..64.psy-ab..0.0.0....0.w_2p_WJHPH4 — Arun, Nov 14 '17 at 08:57
Use a `do ... catch` instead and print the error. It'll probably tell you what's wrong. — JeremyP, Nov 14 '17 at 09:32

score 135 · Accepted Answer · edited Dec 18 '18 at 16:58

135

The problem is that you thought your jsonString is a dictionary. It's not.

It's an array of dictionaries. In raw json strings, arrays begin with [ and dictionaries begin with {.

I used your json string with below code :

let string = "[{\"form_id\":3465,\"canonical_name\":\"df_SAWERQ\",\"form_name\":\"Activity 4 with Images\",\"form_desc\":null}]"
let data = string.data(using: .utf8)!
do {
    if let jsonArray = try JSONSerialization.jsonObject(with: data, options : .allowFragments) as? [Dictionary<String,Any>]
    {
       print(jsonArray) // use the json here     
    } else {
        print("bad json")
    }
} catch let error as NSError {
    print(error)
}

and I am getting the output :

[["form_desc": <null>, "form_name": Activity 4 with Images, "canonical_name": df_SAWERQ, "form_id": 3465]]

edited Dec 18 '18 at 16:58

mfaani

33,269
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answered Nov 14 '17 at 09:19

Amit

4,837
5
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How we get the value from "jsonArray". I am trying if let name = jsonArray["name"] as? String { // no error } which is giving the error "Cannot subscript a value of type '[Dictionary]' with an index of type 'String'" – Android is everything for me May 02 '18 at 11:16
2

@Androidiseverythingforme : That's an array of dictionary, try `let form_name = jsonArray[0]["form_name"] as? String` and you will get the output. – Amit May 02 '18 at 12:22
this was the solution for me too , i was getting a raw json from url , and was unable to read it as an array because it was a string; so the line : " let data = string.data(using: .utf8)! " mentionned in this solution was what solved it , Thank you sir – Taoufik Jun 09 '22 at 10:47

score 40 · Answer 2 · answered May 09 '18 at 01:53

Using JSONSerialization always felt unSwifty and unwieldy, but it is even more so with the arrival of Codable in Swift 4. If you wield a [String:Any] in front of a simple struct it will ... hurt. Check out this in a Playground:

import Cocoa

let data = "[{\"form_id\":3465,\"canonical_name\":\"df_SAWERQ\",\"form_name\":\"Activity 4 with Images\",\"form_desc\":null}]".data(using: .utf8)!

struct Form: Codable {
    let id: Int
    let name: String
    let description: String?

    private enum CodingKeys: String, CodingKey {
        case id = "form_id"
        case name = "form_name"
        case description = "form_desc"
    }
}

do {
    let f = try JSONDecoder().decode([Form].self, from: data)
    print(f)
    print(f[0])
} catch {
    print(error)
}

With minimal effort handling this will feel a whole lot more comfortable. And you are given a lot more information if your JSON does not parse properly.

am I the only one who gets "Type 'Form' does not conform to protocol 'Decodable'" ? — Aviram Netanel, Nov 14 '18 at 13:42
You would have to post your code (in another question, not a comment, there it will look horrible) and your Swift version in order for anyone to help. — Patru, Nov 15 '18 at 02:18

score 16 · Answer 3 · edited May 19 '20 at 17:00

16

I tried the solutions here, and as? [String:AnyObject] worked for me:

do{
    if let json = stringToParse.data(using: String.Encoding.utf8){
        if let jsonData = try JSONSerialization.jsonObject(with: json, options: .allowFragments) as? [String:AnyObject]{
            let id = jsonData["id"] as! String
            ...
        }
    }
}catch {
    print(error.localizedDescription)

}

edited May 19 '20 at 17:00

Zain Ul Abideen

693
10
15

answered Nov 15 '18 at 12:01

Aviram Netanel

12,633
9
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69

`id` is nil for me. – Andor Németh Nov 30 '20 at 15:20

score 7 · Answer 4 · edited Aug 12 '20 at 09:58

I used below code and it's working fine for me. :

let jsonText = "{\"userName\":\"Bhavsang\"}"
var dictonary:NSDictionary?
    
if let data = jsonText.dataUsingEncoding(NSUTF8StringEncoding) {
        
     do {
            dictonary =  try NSJSONSerialization.JSONObjectWithData(data, options: [.allowFragments]) as? [String:AnyObject]
        
            if let myDictionary = dictonary
              {
                  print(" User name is: \(myDictionary["userName"]!)")
              }
            } catch let error as NSError {
            
            print(error)
         }
}

score -1 · Answer 5 · answered Jan 03 '22 at 09:50

-1

static func getJSONStringFromObject(object: Any?) -> String? {
    do {
        let jsonData = try JSONSerialization.data(withJSONObject: object ?? DUMMY_STRING, options: [])
        return String(data: jsonData, encoding: .utf8) ?? DUMMY_STRING
    } catch {
        print(error.localizedDescription)
    }
    return DUMMY_STRING
}

answered Jan 03 '22 at 09:50

Divyansh Jain

373
2
5

this does the oposite from what OP wants – Javier Heisecke Dec 06 '22 at 21:09

Convert Json string to Json object in Swift 4

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