JSON 未解码为结构( fatal error ，Swift)

Question

我正在尝试解码以下 JSON 响应:

{"success":true,"initialprice":"0.00003592","price":"0.00006587",
"high":"0.00006599","low":"0.00003499","volume":"0.68979910",
"bid":"0.00006205","ask":"0.00006595"}

Swift 中的结构如下所示:

struct TOTicker : Codable {
public var success : Bool?
public var initialprice : Double?
public var price : Double?
public var high : Double?
public var low : Double?
public var volume :Double?
public var bid :Double?
public var ask :Double?
}

我用来解码的代码行如下:

let decoder = JSONDecoder()
let ticker = try! decoder.decode(TOTicker.self, from: jsonData)

它一直抛出一个 fatal error ，但我不知道为什么。我以前用这个方法解码没有问题。

Answer 1

首先，要知道错误的原因是什么，您应该执行 do-catch block 而不是 try!:

do {
    let ticker = try decoder.decode(TOTicker.self, from: jsonData)
} catch {
    print(error)
}

因此，您会注意到错误是:

typeMismatch(Swift.Double, Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "initialprice", intValue: nil)], debugDescription: "Expected to decode Double but found a string/data instead.", underlyingError: nil))

这似乎很清楚；您的 json 包含 strings 作为值而不是 double 值(浮点值由“”包围)。您应该做的是将 TOTicker 属性声明为:

struct TOTicker : Codable {
    public var success : Bool?
    public var initialprice : String?
    public var price : String?
    public var high : String?
    public var low : String?
    public var volume :String?
    public var bid :String?
    public var ask :String?
}

现在，您会注意到您能够成功解析它:

let decoder = JSONDecoder()

do {
    let ticker = try decoder.decode(TOTicker.self, from: jsonData)
    print(ticker)
} catch {
    print(error)
}

你应该在日志中看到:

TOTicker(success: Optional(true), initialprice: Optional("0.00003592"), price: Optional("0.00006587"), high: Optional("0.00006599"), low: Optional("0.00003499"), volume: Optional("0.68979910"), bid: Optional("0.00006205"), ask: Optional("0.00006595"))