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如何在swift中解码json对象的命名数组

jsondecoder swift json

Damo · 技术社区 · 8 年前

我有一个json对象的命名数组,通过api调用接收。

{
    "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"
    }]
}

对象是image类型的,我已经定义了它,并且有一个解码函数,可以解码单个图像对象。图像如下:

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
    {
    }
}

我已经为这个场景写了一个测试,但这是我的难处!测试失败(自然)如下:

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?

感谢您的阅读和一如既往的帮助。

2 回复 | 直到 8 年前

Sharad Chauhan Muhammad Bilal Hussain 8 年前

我认为你的编码结构是错误的。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
   }
}

原木:

解码:jsonstructure(图像:[DreamsiteRadio.images(宽度:800.0, 高度:590.0,URL:“ https://obfuscated.image.url/image1.jpg “” DreamsiteRadio.图像(宽度:800.0,高度:533.0,URL: “ https://obfuscated.image.url/image2.jpg “” DreamsiteRadio.图像(宽度:800.0,高度:478.0,URL: “ https://obfuscated.image.url/image3.jpg “)

PGDev 8 年前

您可以创建2个结构来解析完整的响应,而不是1个。

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"
    }
}

由于响应中有嵌套级别,所以我创建了多个结构。

另外,您不需要为解析编写显式容器。 Codable 会自己做的。

你可以简单地解码样本 JSON 用:

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