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")

Use a do ... catch instead and print the error. It'll probably tell you what's wrong. — JeremyP
– JeremyP, Commented Nov 14, 2017 at 9:32

mfaani · Accepted Answer · 2018-12-18 16:58:10Z

139

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, 2018 at 16:58

mfaani

37k20 gold badges195 silver badges329 bronze badges

answered Nov 14, 2017 at 9:19

Amit

4,8965 gold badges35 silver badges48 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Android is everything for me Over a year ago

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<String, Any>]' with an index of type 'String'"

Amit Over a year ago

@Androidiseverythingforme : That's an array of dictionary, try let form_name = jsonArray[0]["form_name"] as? String and you will get the output.

Taoufik Over a year ago

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

Patru · Accepted Answer · 2018-05-09 01:53:17Z

42

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.

answered May 9, 2018 at 1:53

Patru

4,5692 gold badges36 silver badges44 bronze badges

3 Comments

Aviram Netanel Over a year ago

am I the only one who gets "Type 'Form' does not conform to protocol 'Decodable'" ?

Patru Over a year ago

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.

AndiAna Over a year ago

remove "import Cocoa" for Swift 5 then it works. thanks!

Zain Ul Abideen · Accepted Answer · 2020-05-19 17:00:42Z

17

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, 2020 at 17:00

Zain Ul Abideen

78311 silver badges16 bronze badges

answered Nov 15, 2018 at 12:01

Aviram Netanel

13.8k9 gold badges50 silver badges73 bronze badges

1 Comment

Andor Németh Over a year ago

id is nil for me.

Dohab · Accepted Answer · 2020-08-12 09:58:41Z

8

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)
         }
}

edited Aug 12, 2020 at 9:58

Dohab

4455 silver badges16 bronze badges

answered Sep 17, 2019 at 11:05

Bhavsang Jam

3844 silver badges12 bronze badges

Comments

Divyansh Jain · Accepted Answer · 2022-01-03 09:50:34Z

-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 3, 2022 at 9:50

Divyansh Jain

3702 silver badges6 bronze badges

1 Comment

Javier Heisecke Over a year ago

this does the oposite from what OP wants

Collectives™ on Stack Overflow

Convert Json string to Json object in Swift 4

5 Answers 5

3 Comments

3 Comments

1 Comment

Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

3 Comments

3 Comments

1 Comment

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related