Force AnyCodable to change a type of an object

transmute.swift

import Foundation
import AnyCodable

// This is Fugly but it get the job done.
extension AnyCodable {
  func transmuteThrow<Output: Codable>(_ encoder: JSONEncoder = JSONEncoder(), _ decoder: JSONDecoder = JSONDecoder()) throws -> Output {
    let data = try encoder.encode(self)
    return try decoder.decode(Output.self, from: data)
  }
  
  // obj.value.transmute(encoder, decoder) as [ThumbnailField]?
  func transmute<Output: Codable>(_ encoder: JSONEncoder = JSONEncoder(), _ decoder: JSONDecoder = JSONDecoder()) -> Output? {
    return try? transmuteThrow(encoder, decoder)
  }
}