Decoding Json to get string value

Question

I am trying to get string value in a json but I keep getting nil.

This is json structure

{
    "user": {
        "password": "...",
        "name": "...",
        "authToken": "...",
        "events": [
            {
                "uuid": (int)
            }
        ]
    }
}

this is how I am decoding.

do {
       let json = try JSONSerialization.jsonObject(with: responseData, options:[]) as! [String : Any?]

       let authToken: String = json["authToken"] as! String

       print(authToken)

   } catch let error {
       print(error)
   }

but I keep getting nil value in my console

Use Codable and JSONDecoder. Do not use the legacy JSONSerialization and force casting. In any case, you need to decode several levels, you cannot just access authToken, which is nested inside the user Dictionary of the JSON. — David Pasztor
– David Pasztor, Commented Mar 4, 2020 at 15:19
As pointed by others, your top-level key on your json object is "user". — lazi74
– lazi74, Commented Mar 4, 2020 at 15:26

Shehata Gamal · Accepted Answer · 2020-03-04 15:38:47Z

1

You need

let user = json["user"] as! [String:Any] 
let authToken = user["authToken"] as! String

edited Mar 4, 2020 at 15:38

answered Mar 4, 2020 at 15:20

Shehata Gamal

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Comments

Dmitriy Lupych · Accepted Answer · 2020-03-04 15:28:00Z

0

You can access authToken using chaining transformations like this:

let json = try JSONSerialization.jsonObject(with: responseData, options:[]) as? [String : Any]

let authToken = json
    .flatMap { $0["user"] as? [String: Any] }
    .flatMap { $0["authToken"] as? String }

In the end, you will have an optional authToken property. If JSON is valid and authToken exists, you can unwrap it and reach the value!

answered Mar 4, 2020 at 15:28

Dmitriy Lupych

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3 Comments

David Pasztor Over a year ago

Don't use flatMap with Optional values, that's deprecated already. Moreover, using flatMap or compactMap to get the value of a single key from a Dictionary is a really bad idea - and your current implementation won't even work, since that flatMap would iterate over all key-value pairs of the Dictionary.

Dmitriy Lupych Over a year ago

Hello! Function .flatMap is deprecated on Array (now you should use .compactMap), but not Optional type. Using Codable protocol is a better idea, I know. But in this case - just for testing, why we can't use provided answer?

Dmitriy Lupych Over a year ago

I think you've missed, that in my case, .flatMap acts on Optional type, but not on Dictionary. It will not iterate through the collection, it will just perform the transformation, in case the value is not nil.

Toto · Accepted Answer · 2020-03-04 15:39:22Z

0

Create this Object model:

import Foundation

// MARK: - Matrix
struct Matrix: Codable {
    let user: User
}

// MARK: - User
struct User: Codable {
    let password, name, authToken: String
    let events: [Event]
}

// MARK: - Event
struct Event: Codable {
   let uuid: Int
}

Use it like this:

do {
    let matrix = try JSONDecoder().decode(Matrix.self, from: jsonData)
    let token = matrix.user.authToken
} catch let error {
    print(error.localizedDescription)
}

replace Matrix with your desire object name

edited Mar 4, 2020 at 15:39

answered Mar 4, 2020 at 15:22

Toto

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2 Comments

David Pasztor Over a year ago

Don't use try? to mask errors. Use try inside a do-catch block.

Toto Over a year ago

updated my answer, though is obvious that it should use the safest way

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