keynotfound on id decoding JSON

Question

I'm getting the following error when trying to decode JSON. What's odd is I've used similar code on other endpoints and no issue using UUID.

error:

keyNotFound(CodingKeys(stringValue: "id", intValue: nil), Swift.DecodingError.Context(codingPath: [_JSONKey(stringValue: "Index 0", intValue: 0)], debugDescription: "No value associated with key CodingKeys(stringValue: "id", intValue: nil) ("id").", underlyingError: nil))

Here's my class

class Api: ObservableObject {
@State private var showingAlert = false

// completion handler for JSON Data
func getUserData(url: String, completion : @escaping ([RunClubsv2])->()){

    let session = URLSession(configuration: .default)

    session.dataTask(with: URL(string: url)!) { (data, _, err) in

        if err != nil{

            print(err!.localizedDescription)
            return
        }
        //decoding JSON

        do {

            let users = try JSONDecoder().decode([RunClubsv2].self, from: data!)
            print(users)
            //returning data
            completion(users)

        }
        catch{
            print(error)
        }
    }
.resume()
}

Here's my UI code


    @State var runclubv2: [RunClubsv2] = []

    var body: some View {
        VStack {
            if runclubv2.isEmpty{
                Text("damn it")
            }
            else {

                //display data
                List(runclubv2) { runclubv2 in
                    Text(runclubv2.name)
                }

            }

        }
        .onAppear{
            Api().getUserData(url: "<URL EndPoint>") { ([RunClubsv2]) in
                self.runclubv2 = self.runclubv2
            }
        }
    }
}

Here's the response data

[
    {
        "name": "Joggers for Lagers",
        "location": "Amor Artis Brewery, Fort Mill",
        "date": "6:30 PM",
        "category": "Monday"
    },
    {
        "name": "Old Armor Run Club",
        "location": "Kannapolis",
        "date": "6:00 PM",
        "category": "Monday"
    }
]

You have an `id` property in your `RunClubsv2` struct which probably needs to be optional :) — gcharita, Sep 08 '20 at 20:03
Create a CodingKey enum that contain only the properties you get from json (which does not include id I assume) so `enum CodingKeys: String, CodingKey { case name, location, date, category }` — Joakim Danielson, Sep 08 '20 at 20:10
@Robert you can generate `id` manually (if you need it) and not decoding it from the JSON because it does not exist there. — gcharita, Sep 08 '20 at 20:22
I am sorry, I am late. https://stackoverflow.com/a/75403761/10758321 — 钟智强, Feb 09 '23 at 19:53

score 2 · Answer 1 · answered Sep 08 '20 at 20:10

2

Please read the JSON carefully. Where is the key id? That’s exactly what the error message says.

I guess your struct conforms to Identifiable with a hard-coded UUID. If so you have to add CodingKeys to exclude id from being decoded.

answered Sep 08 '20 at 20:10

vadian

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I don't understand. I have a similar API call with a similar `struct` and I don't get this error and I don't have an `id` included. – Robert Sep 08 '20 at 20:17
The error is clear. The decoder tries to decode a key `id` which obviously doesn’t exist in the JSON. Therefore you have to add `CodingKeys`... – vadian Sep 08 '20 at 20:25
Yeah I can read :). What I don't understand is how I can have two similar functions with similar struct's and one works and one doesn't. – Robert Sep 08 '20 at 20:32
1

Similar is not equal – vadian Sep 08 '20 at 20:35

钟智强 · Answer 2 · 2023-02-09T20:12:30.413

I believe the id needs to be optional. So what happened in your code was that the JSON_VALUE was trying to write into the id key which obviously from what you show us is that there's no key named id.

I assumed that you might also face this following error:

Fatal error: 'try!' expression unexpectedly raised an error: Swift.DecodingError.keyNotFound(CodingKeys(stringValue: "id", intValue: nil), Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "data", intValue: nil), _JSONKey(stringValue: "Index 0", intValue: 0)], debugDescription: "No value associated with key CodingKeys(stringValue: \"id\", intValue: nil) (\"id\").", underlyingError: nil))

The error is very straightforward No value associated with key CodingKeys(stringValue: \"id\", intValue: nil) (\"id\").

This can be solved.

Your current code must be:

struct RunClubsv2 {
    public var name :String
    public var location :String
    public var date :String
    public var category :String

}

The problem is from this line here public var name :String, which can avoid the error by adding a ? after the String or String?. Which means you are making that optional or nullable.

Lastly, your updated code should be something like this:

struct RunClubsv2 {
    public var name :String?
    public var location :String
    public var date :String
    public var category :String

}

keynotfound on id decoding JSON

2 Answers2