Swift Json decoding with unsure incoming data-CodePudding

I'm struggeling to decode some Json data in swift.

My back-end api will return me either an array of X or an object with (at least) one property named "items" of type array of X.

I've searched but found no solutions. Do you have any ?

struct A: Decodable {
   var items: [X]
   // some other optional properties

   public init(from decoder: Decoder) throws {
       // Sometimes I receive the correct A object
       // Sometimes I only receive the array of X without the surrounding object of type A.
   }
}

And to make things worst, I'm bound to decode like I was always receiving an object of typa A... :

myObjectOfTypeA = try decoder.decode(A.self, from: data)

Most of the time, I'll receive a proper A object like this :

{
    "items": 
    [
        {
            "id": 7,
            "startsOn": "2021-03-01",
            "endsOn": "2021-12-31"
        },
        {
            "id": 6,
            "startsOn": "2021-04-19",
            "endsOn": "2022-04-04"
        }
    ],
    "next": null,
    "prev": null,
    "count": 2
}

But sometimes, I'll receive only the items array like this :

[
    {
        "id": 7,
        "startsOn": "2021-03-01",
        "endsOn": "2021-12-31"
    },
    {
        "id": 6,
        "startsOn": "2021-04-19",
        "endsOn": "2022-04-04"
    }
]

Any ideas would be greatly appreciated because I'm clearly out of ideas myself...