安全 JSON 解码。仍然找不到密钥：没有与密钥关联的值'

Question

IMGUR 图片搜索 returns json:

    {"data": [{
                "title": "Family :)",
               "images": [{
                    "title": null,
                    "description": null,
                    "nsfw": null,
                    "link": "https:\/\/i.imgur.com\/oe5BrCu.jpg",
            }]
        } ]
    }

模型对象已配置：

struct ImgurResponse: Codable {
    let data: [ImageData]
}

struct ImageData: Codable {
    let title: String
    let images: [Image]
}

struct Image: Codable {
    let title, description, nsfw: String
    let link: String
    
    enum CodingKeys: String, CodingKey {
        case title
        case description
        case nsfw
        case link
    }
    
    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        title = try container.decodeIfPresent(String.self, forKey: .title) ?? ""
        description = try container.decodeIfPresent(String.self, forKey: .description) ?? ""
        nsfw = try container.decodeIfPresent(String.self, forKey: .nsfw) ?? ""
        link = try container.decodeIfPresent(String.self, forKey: .link) ?? ""
    }

调用 JSONDecoder():

let response = try JSONDecoder().decode(ImgurResponse.self, from: data)

在最后一行设置刹车点时'link = '我在上面降落了大约 48 次。据我了解，我们能够创建 Image 对象 48 次。

但是，我遇到了一个错误，'response' 没有创建：

Key 'CodingKeys(stringValue: "images", intValue: nil)' not found: No value associated with key CodingKeys(stringValue: "images", intValue: nil) ("images").
codingPath: [CodingKeys(stringValue: "data", intValue: nil), _JSONKey(stringValue: "Index 49", intValue: 49)]

我还应该实施哪些 'safe' 解码实践？

Answer 1

错误意味着您映射到 ImageData 的 JSON 对象之一缺少键 "images"，但 ImageData 期望它在那里，因为这不是可选的。

要修复，您需要将属性 images 设为可选：

struct ImageData: Codable {
   let title: String
   let images: [Image]? // <- here
}

通常，可选数组很难使用，因此您可能需要考虑在缺少键时创建一个空数组：

struct ImageData {
   let title: String
   let images: [Image]
}

extension ImageData: Codable {
   init(from decoder: Decoder) throws {
      let container = try decoder.container(keyedBy: CodingKeys.self)
        
      title = try container.decode(String.self, forKey: .title)
      images = try container.decodeIfPresent([Image].self, forKey: .images) ?? []
   }
}

安全 JSON 解码。仍然找不到密钥：没有与密钥关联的值'

Safe JSON Decoding. Still getting Key not found: No value associated with key'

json

swift

swift4

codable