如何解码 Swift 中 json 对象的命名数组

Question

我有一个 json 对象的命名数组，我通过 API 调用接收到它。

{
    "Images": [{
        "Width": 800,
        "Height": 590,
        "Url": "https://obfuscated.image.url/image1.jpg"
        }, {
        "Width": 800,
        "Height": 533,
        "Url": "https://obfuscated.image.url/image2.jpg"
        }, {
        "Width": 800,
        "Height": 478,
        "Url": "https://obfuscated.image.url/image3.jpg"
    }]
}

这些对象是我定义的图像类型，并具有解码功能，可以解码单个图像对象。图片看起来像：

struct Image : Codable {
    let width: CGFloat
    let height: CGFloat
    let url: String

    enum ImageKey: String, CodingKey {
        case width = "Width"
        case height = "Height"
        case url = "Url"
    }

    init(from decoder: Decoder) throws
    {
        let container = try decoder.container(keyedBy: ImageKey.self)
        width = try container.decodeIfPresent(CGFloat.self, forKey: .width) ?? 0.0
        height = try container.decodeIfPresent(CGFloat.self, forKey: .height) ?? 0.0
        url = try container.decodeIfPresent(String.self, forKey: .url) ?? ""
    }

    func encode(to encoder: Encoder) throws
    {
    }
}

我已经为这个场景编写了一个测试，但这就是我难过的地方！测试失败（自然），看起来像这样：

func testManyImages() throws {

    if let urlManyImages = urlManyImages {
        self.data = try? Data(contentsOf: urlManyImages)
    }

    let jsonDecoder = JSONDecoder()
    if let data = self.data {
        if let _images:[Image] = try? jsonDecoder.decode([Image].self, from: data) {
            self.images = _images
        }
    }

    XCTAssertNotNil(self.images)
}

我的问题是：

如何通过名称 "Images" 或其他方式访问图像数组？

感谢阅读，一如既往地感谢您的帮助。

Answer 1

我认为你的 Codable 结构是错误的。应该是：

struct JSONStructure: Codable {
    let images: [Images]
    private enum CodingKeys: String, CodingKey {
        case images = "Images"
    }
}

struct Images: Codable {
    let width: CGFloat
    let height: CGFloat
    let url: String

    private enum CodingKeys: String, CodingKey {
        case width  = "Width"
        case height = "Height"
        case url    = "Url"
    }

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        width         = try container.decodeIfPresent(CGFloat.self, forKey: .width) ?? 0.0
        height        = try container.decodeIfPresent(CGFloat.self, forKey: .height) ?? 0.0
        url           = try container.decodeIfPresent(String.self, forKey: .url) ?? ""
    }

    func encode(to encoder: Encoder) throws {
    }
}

然后：

if let data = self.data {
   if let decoded = try? jsonDecoder.decode(JSONStructure.self, from: data) {
       print("Decoded : \(decoded)")
       self.images = decoded.images
   }
}

日志：

Decoded : JSONStructure(images: [DreamSiteradio.Images(width: 800.0, height: 590.0, url: "https://obfuscated.image.url/image1.jpg"), DreamSiteradio.Images(width: 800.0, height: 533.0, url: "https://obfuscated.image.url/image2.jpg"), DreamSiteradio.Images(width: 800.0, height: 478.0, url: "https://obfuscated.image.url/image3.jpg")])

Answer 2

您可以创建 2 个结构而不是 1 个来解析完整的响应，即

struct Response: Codable
{
    let images: [Image]?
    enum CodingKeys: String, CodingKey
    {
        case images = "Images"
    }
}
struct Image : Codable
{
    var width: CGFloat?
    let height: CGFloat?
    let url: String?

    enum CodingKeys: String, CodingKey
    {
        case width = "Width"
        case height = "Height"
        case url = "Url"
    }
}

由于响应中存在嵌套级别，这就是我创建多个结构的原因。

此外，您无需编写显式解析容器。 Codable 会自己做。

您可以简单地解码示例 JSON：

if let data = jsonStr.data(using: .utf8)
{
    let response = try? JSONDecoder().decode(Response.self, from: data)
    print(response?.images)
}

如何解码 Swift 中 json 对象的命名数组

How to decode a named array of json objects in Swift

json

swift

jsondecoder