Decoding an Array in a Swift model (Decodable)

Question

I am retrieving a JSON from an API and I wanted to make a Model for each endpoints I use.

All the endpoints use this format:

{
  "id": "xxxxxx",
  "result": {…},
  "error": null
}

The keys are:

id is always a string
error can be null or an object with keys in it
result can be either null; an object or an array.

The problem I am encountering is that on one of the endpoints the results are arrays of array:

{
  "id": "xxxxxx",
  "result": [
      [
          "client_id",
          "name",
          50,
          "status"
      ]
  ],
  "error": null
}

As you can see, I have arrays of array where the values can be either a String or Int.

How do you decode this using Decodable protocol and then using those decoded values as String or Int depending on their origin values?

Check this answer: https://stackoverflow.com/a/48388443/8447312 — emrepun, Dec 23 '18 at 20:45
Show us the Decodable struct or class that you are using. We can't fix your code if you don't show your code. — EmilioPelaez, Dec 23 '18 at 20:53
The simplest solution is to use two separate models. It's normal that different endpoints return different data models. — Sulthan, Dec 23 '18 at 21:28

score 5 · Accepted Answer · edited May 01 '20 at 14:51

5

import Foundation

let string =  """
{
    "id": "xxxxxx",
    "result": [
        [
            "client_id",
            "name",
            50,
            "status"
        ]
    ],
    "error": null
}
"""

struct Container: Codable {
    let id: String
    let result: [[Result]]
    let error: String?
}

enum Result: Codable {
    case integer(Int)
    case string(String)

    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        if let x = try? container.decode(Int.self) {
            self = .integer(x)
            return
        }
        if let x = try? container.decode(String.self) {
            self = .string(x)
            return
        }
        throw DecodingError.typeMismatch(Result.self, DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Wrong type for Result"))
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()
        try container.encode(self)
    }
}

let jsonData = string.data(using: .utf8)!
let container = try? JSONDecoder().decode(Container.self, from: jsonData)

print(container)

improved @ArinDavoodian's answer.

To read the data:

container?.result.first?.forEach { object in
    switch object {
    case let .integer(intValue):
        print(intValue)
        break
    case let .string(stringValue):
        print(stringValue)
        break
    }
}

a simple solution:

let yourInsideArray = container?.result.first!
for index in 0..<yourInsideArray.count {
let yourObjectInsideThisArray = yourInsideArray[i]
//do some
 switch yourObjectInsideThisArray {
    case let .integer(intValue):
        print(intValue)
        break
    case let .string(stringValue):
        print(stringValue)
        break
    }
}

edited May 01 '20 at 14:51

nacho4d

43,720
45
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240

answered Dec 23 '18 at 21:14

Vyacheslav

26,359
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why not simply `func encode(to encoder: Encoder) throws { var container = encoder.singleValueContainer() try container.encode(self) }` – Leo Dabus Dec 23 '18 at 22:11
Funny think playground works but shows (12716 times) instead of 4 – Leo Dabus Dec 23 '18 at 22:20
you can simplify your decoder also `init(from decoder: Decoder) throws { let container = try decoder.singleValueContainer() try self = (try? .integer(container.decode(Int.self))) ?? .string(container.decode(String.self)) }` – Leo Dabus Dec 23 '18 at 22:21
In my playground just 4 times – Vyacheslav Dec 23 '18 at 22:23
I might need a new playground file kkk to many code on it probablyt – Leo Dabus Dec 23 '18 at 22:23
About your second suggestion. Imho, too complecated for production code. – Vyacheslav Dec 23 '18 at 22:24
Well that's how I got an error: how do you access the data into the result array? I just can't convert the model to a String: `Cannot convert value of type 'HostListModel.Result?' to type 'String' in coercion`. Thanks. – Anthony Dec 23 '18 at 23:35
@Anthony you have to unwrap enums using a specific Swift syntax. I've updated my post. – Vyacheslav Dec 23 '18 at 23:39
Thanks @Vyacheslav, it works. One last thing then: how do you read the data without a forEach loop? Thanks again. – Anthony Dec 23 '18 at 23:56
Awesome. Thanks for the quick replies! – Anthony Dec 24 '18 at 00:01
@Anthony have a nice day! – Vyacheslav Dec 24 '18 at 00:01

Decoding an Array in a Swift model (Decodable)

1 Answers1