medium-codable-lossyarray.swift

struct LossyArray<Element: Decodable>: Decodable {
  private(set) var elements: [Element]

  init(from decoder: Decoder) throws {
    var container = try decoder.unkeyedContainer()
    var elements = [Element]()

    if let count = container.count {
      elements.reserveCapacity(count)
    }

    while !container.isAtEnd {
      do {
        let element = try container.decode(Element.self)
        elements.append(element)
      }
      catch let error {
        print("failed to decode \(Element.self): \(error)")
        // Decode as the dummy DiscardedElement type to skip it.
        _ = try? container.decode(DiscardedElement.self)
        continue
      }
    }

    self.elements = elements
  }
}

struct DiscardedElement: Codable {}

// Usage example
class AuthorsResponse: Decodable {
  let array: [Author]

  enum CodingKeys: CodingKey {
    case response
  }

  required init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    self.array = try container.decode(LossyArray<Animal>.self, forKey: .response).elements
  }
}