如何正确解析带有根元素的 JSON 作为 Swift 中的数组？

Question

我有以下问题，我没有正确的结构来解码来自 node-red 的响应以了解我的 Sonos 播放器的状态：

[[{"urlHostname":"192.168.1.1","urlPort":1400,"baseUrl":"http://192.168.1.1:1400","sonosName":"Sonos1","uuid":"RINCON_SONOS14001400","invisible":false},{"urlHostname":"192.168.1.2","urlPort":"1400","baseUrl":"http://192.168.1.2:1400","sonosName":"Sonos2","uuid":"RINCON_SONOS21400","invisible":false},{"urlHostname":"192.168.1.3","urlPort":"1400","baseUrl":"http://192.168.1.3:1400","sonosName":"Sonos3","uuid":"RINCON_SONOS31400","invisible":false},{"urlHostname":"192.168.1.4","urlPort":"1400","baseUrl":"http://192.168.1.4:1400","sonosName":"Sonos4","uuid":"RINCON_SONOS41400","invisible":false},{"urlHostname":"192.168.1.5","urlPort":"1400","baseUrl":"http://192.168.1.5:1400","sonosName":"Sonos5","uuid":"RINCON_SONOS51400","invisible":false},{"urlHostname":"192.168.1.6","urlPort":"1400","baseUrl":"http://192.168.1.6:1400","sonosName":"Sonos6","uuid":"RINCON_SONOS61400","invisible":false}]]

我的结构和解码调用如下所示：

typealias Response = [sonosData]

struct sonosData: Codable {
    let  sonos: [sonosStatusEntry]?
}

struct sonosStatusEntry: Codable {
    let status: [sonosStatus]?
}

struct sonosStatus: Codable {
    let urlHostname: String
    let urlPort: Int
    let baseUrl: String
    let sonosName: String
    let uuid: String
    let invisible: Bool
}

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

我在 Swift 中收到以下错误：

Failed to load: The data couldn’t be read because it isn’t in the correct format.

有什么建议吗？

Answer 1

您的代码有 2 个错误：

1. 您要解码的数据是[[sonosStatus]]。所以你需要解码为：

let response = try JSONDecoder().decode([[sonosStatus]].self, from: data)

1. urlPort 代表 String 和 Int。因此，您需要更正 JSON 格式或使用自定义解码器支持这两种格式。

您可以使用这个简单的属性包装器来实现：

@propertyWrapper
struct SomeKindOfInt: Codable {
    var wrappedValue: Int?

    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        if let stringifiedValue = try? container.decode(String.self) {
            wrappedValue = Int(stringifiedValue)
        } else {
            wrappedValue = try container.decode(Int.self)
        }
    }
}

然后像这样使用它：

struct sonosStatus: Codable {
    let urlHostname: String
    @SomeKindOfInt var urlPort: Int?
    let baseUrl: String
    let sonosName: String
    let uuid: String
    let invisible: Bool
}

Answer 2

其中一个问题与urlPort 有关。您的 json 具有 Int 和 String 的 urlPort 值。您可以定义自定义初始化来处理它。

struct sonosStatus: Codable {
    let urlHostname: String
    let urlPort: Int
    let baseUrl: String
    let sonosName: String
    let uuid: String
    let invisible: Bool    
    
    init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)
        urlHostname = try values.decode(String.self, forKey: .urlHostname)
        baseUrl = try values.decode(String.self, forKey: .baseUrl)
        sonosName = try values.decode(String.self, forKey: .sonosName)
        uuid = try values.decode(String.self, forKey: .uuid)
        invisible = try values.decode(Bool.self, forKey: .invisible)
        
        // you can define urlPort as optional or unwrap it.
        if let intVal = try? values.decode(Int.self, forKey: .urlPort) {
            urlPort = intVal
        } else if let stringVal = try? values.decode(String.self, forKey: .urlPort) {
            urlPort = Int(stringVal) ?? 0
        } else {
            urlPort = ""
        }
    }
}

而且你的 json 是一个 sonosStatus 数组。

所以你需要修改Response typealias，如下所示：

typealias Response = [[sonosStatus]]

Answer 3

您可以将 JSONSerialization 与 .allowFragments 读取选项一起使用。

let objects = (try?JSONSerialization.jsonObject(with: data, options: .allowFragments)) as? [[NSDictionary]]

它已在最新的 Swift 版本上得到修复：https://bugs.swift.org/browse/SR-6163