Do you need to decode your JSON to [String: Any]? Here is how you can do this.

Requirements

Answer is that you cannot do this using Any type. You need specify something more concrete than Any.

Dictionary is automatically decodable if its elements are decodable. Type Any is not decodable.

However if you are looking for the answer it means that you actually have some kind of JSON which needs to be handled somehow. The topic is also related to array like [Any].

Solution

You need to specify finite number of possible values of your Any type. For example we expect that there are two different structures like following:

struct Payload: Codable {
    let id: String
    let eventName: String
    let metadata: [Metadata]
}

struct Metadata: Codable {
    let name: String?
    let price: Double?
    let rating: Int?
}

But of course you cannot do

let decodedData = try JSONDecoder().decode([String: Any].self, from: json.data(using: .utf8)!)

because there is used type Any.

First of all we need to figure out how JSON for this dictionary possibly looks like. It would be sth like this:

{
    "keyNumber1": {
        "type": "payload",
        "data": {
            "id": "someId1",
            "eventName": "Event Name 1",
            "metadata": []
        }
    },
    "keyNumber2": {
        "type": "metadata",
        "data": {
            "name": "Metadata Name",
            "price": 123.4,
            "rating": 100
        }
    }
}

Then it's simple because you need to define enum instead of your Any type like follows:

enum DataType: String, Codable {
    case payload
    case metadata
}

enum MyValue: Decodable {
    case payload(_ payload: Payload)
    case metadata(_ metadata: Metadata)

    private enum CodingKeys: String, CodingKey {
        case `type`
        case `data`
    }

    init(from decoder: Decoder) throws {
        let map = try decoder.container(keyedBy: CodingKeys.self)
        let dataType = try map.decode(DataType.self, forKey: .type)
        switch dataType {
        case .payload:
            self = .payload(try map.decode(Payload.self, forKey: .data))
        case .metadata:
            self = .metadata(try map.decode(Metadata.self, forKey: .data))
        }
    }
}

And decode JSON using following code:

let decodedData = try JSONDecoder().decode([String: MyValue].self, from: json.data(using: .utf8)!)

Full Playground code:

Blog

How to make Swift's [String: Any] decodable?

Ariel Bogdziewicz

Requirements

Solution

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