处理包含多种类型的JSON数组-Swift 4 Decodable

Question

我正在尝试使用Swift 4 Decodable解析包含两种不同类型对象的数组。数据看起来像这样，其中的included数组是包含Member和ImageMedium对象的数组：

{
  "data": [{
    "id": "8f7cbbac-c133-4b5e-a2ec-1f32353018fa",
    "type": "post",
    "title": "Test Post 1",
    "owner-id": "8986563c-438c-4d77-8115-9e5de2b6e477",
    "owner-type": "member"
  }, {
    "id": "f6b3c640-a58b-449f-93c7-f6cb7b569a9c",
    "type": "post",
    "title": "Test Post 2",
    "owner-id": "38d845a4-db66-48b9-9c15-d857166e255e",
    "owner-type": "member"
  }],
  "included": [{
    "id": "8986563c-438c-4d77-8115-9e5de2b6e477",
    "type": "member",
    "first-name": "John",
    "last-name": "Smith"
  }, {
    "id": "d7218ca1-de53-4832-bb8f-dbceb6747e98",
    "type": "image-medium",
    "asset-url": "https://faketest.com/fake-test-1.png",
    "owner-id": "f6b3c640-a58b-449f-93c7-f6cb7b569a9c",
    "owner-type": "post"
  }, {
    "id": "c59b8c72-13fc-44fd-8ef9-4b0f8fa486a0",
    "type": "image-medium",
    "asset-url": "https://faketest.com/fake-test-2.png",
    "owner-id": "8f7cbbac-c133-4b5e-a2ec-1f32353018fa",
    "owner-type": "post"
  }, {
    "id": "38d845a4-db66-48b9-9c15-d857166e255e",
    "type": "member",
    "first-name": "Jack",
    "last-name": "Doe"
  }]
}

我尝试了多种方法来使用Decodable干净地解决此问题，但是到目前为止，对我唯一有效的方法是为一个结构Included包含两个对象的所有属性作为可选属性，如下所示：

struct Root: Decodable {
    let data: [Post]?
    let included: [Included]?
}

struct Post: Decodable {
    let id: String?
    let type: String?
    let title: String?
    let ownerId: String?
    let ownerType: String?

    enum CodingKeys: String, CodingKey {
        case id
        case type
        case title
        case ownerId = "owner-id"
        case ownerType = "owner-type"
    }
}

struct Included: Decodable {
    let id: String?
    let type: String?
    let assetUrl: String?
    let ownerId: String?
    let ownerType: String?
    let firstName: String?
    let lastName: String?

    enum CodingKeys: String, CodingKey {
        case id
        case type
        case assetUrl = "asset-url"
        case ownerId = "owner-id"
        case ownerType = "owner-type"
        case firstName = "first-name"
        case lastName = "last-name"
    }
} 

这可以通过实现创建工作的方法Member和ImageMedium对象从Included基于关闭它的结构是什么type属性，但是这显然不够理想。我希望有一种使用custom来完成此任务的方法init(from decoder: Decoder)，但是我还没有开始使用它。有任何想法吗？

Answer 1

我想出了如何将混合included数组解码为每种类型的两个数组。与使用一种可覆盖多种数据类型的结构相比，使用两种可分解的结构更易于处理且用途更广。

这是我对任何感兴趣的人的最终解决方案：

struct Root: Decodable {
    let data: [Post]?
    let members: [Member]
    let images: [ImageMedium]

    init(from decoder: Decoder) throws {

        let container = try decoder.container(keyedBy: CodingKeys.self)

        data = try container.decode([Post].self, forKey: .data)

        var includedArray = try container.nestedUnkeyedContainer(forKey: .included)
        var membersArray: [Member] = []
        var imagesArray: [ImageMedium] = []

        while !includedArray.isAtEnd {

            do {
                if let member = try? includedArray.decode(Member.self) {
                    membersArray.append(member)
                }
                else if let image = try? includedArray.decode(ImageMedium.self) {
                    imagesArray.append(image)
                }
            }
        }
        members = membersArray
        images = imagesArray
    }

    enum CodingKeys: String, CodingKey {
        case data
        case included
    }
}

struct Post: Decodable {
    let id: String?
    let type: String?
    let title: String?
    let ownerId: String?
    let ownerType: String?

    enum CodingKeys: String, CodingKey {
        case id
        case type
        case title
        case ownerId = "owner-id"
        case ownerType = "owner-type"
    }
}

struct Member: Decodable {
    let id: String?
    let type: String?
    let firstName: String?
    let lastName: String?

    enum CodingKeys: String, CodingKey {
        case id
        case type
        case firstName = "first-name"
        case lastName = "last-name"
    }
}

struct ImageMedium: Decodable {
    let id: String?
    let type: String?
    let assetUrl: String?
    let ownerId: String?
    let ownerType: String?

    enum CodingKeys: String, CodingKey {
        case id
        case type
        case assetUrl = "asset-url"
        case ownerId = "owner-id"
        case ownerType = "owner-type"
    }
}