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?

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
– EmilioPelaez, Commented Dec 23, 2018 at 20:53
The simplest solution is to use two separate models. It's normal that different endpoints return different data models. — Sulthan
– Sulthan, Commented Dec 23, 2018 at 21:28

nacho4d · Accepted Answer · 2020-05-01 14:51:37Z

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 1, 2020 at 14:51

nacho4d

45.5k47 gold badges164 silver badges246 bronze badges

answered Dec 23, 2018 at 21:14

Vyacheslav

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11 Comments

Leo Dabus Over a year ago

why not simply

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

Leo Dabus Over a year ago

Funny think playground works but shows (12716 times) instead of 4

Leo Dabus Over a year ago

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))     }

Vyacheslav Over a year ago

In my playground just 4 times

Leo Dabus Over a year ago

I might need a new playground file kkk to many code on it probablyt

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