Question

我正在尝试通过API调用来访问fixer.io。这是我第一次尝试这样做，但是我没有得到想要的结果。我想从此JSON文件中获取“费率”和“结果”。

{
    "success": true,
    "query": {
        "from": "GBP",
        "to": "JPY",
        "amount": 25
    },
    "info": {
        "timestamp": 1519328414,
        "rate": 148.972231
    },
    "historical": ""
    "date": "2018-02-22"
    "result": 3724.305775
}

我实现的方法就是这种方法，但是我无法弄清楚在进行此API调用时如何检索“比率”和“结果”。

extension APIsRuler {
  func getExchangeRate(from: String, to: String, amount: String, callback: @escaping (Bool, ConversionResult?) -> Void) {
    var request = URLRequest(url: APIsRuler.exchangeURL)
    let body = "convert?access_key=\(APIsRuler.exchangeAPI)&from=\(from)&to=\(to)&amount=\(amount)"
    request.httpMethod = "GET"
    request.httpBody = body.data(using: .utf8)
    let session = URLSession(configuration: .default)

    task?.cancel()
    task = session.dataTask(with: request) { (data, response, error) in
      DispatchQueue.main.async {
        guard let data = data, error == nil else {
          return callback(false, nil)
        }
        guard let response = response as? HTTPURLResponse, response.statusCode == 200 else {
          return callback(false, nil)
        }
        guard let responseJSON = try? JSONDecoder().decode([String: Double].self, from: data),
          let rate = responseJSON["rate"],
          let result = responseJSON["result"] else {
            return callback(false, nil)
        }
        let conversionResult = ConversionResult(exchangeRate: rate, exchangeResult: result)
        callback(true, conversionResult)
      }
    }
    task?.resume()
  }
}

Answer 1

使用真实的模型对象，如下所示：

struct Conversion: Codable {
    let success: Bool
    let query: Query
    let info: Info
    let historical, date: String
    let result: Double
}

struct Info: Codable {
    let timestamp: Int
    let rate: Double
}

struct Query: Codable {
    let from, to: String
    let amount: Int
}

并使用JSONDecoder解析您的回复：

do {
  let conversion = try JSONDecoder().decode(Conversion.self, from: data)
  let rate = conversion.info.rate
  let result = conversion.result
} catch { print(error) }

Answer 2

您正在混合使用两种不同的API。

使用 JSONSerialization ，结果是一个字典，您可以通过键和索引订阅获得值。而且您必须向下转换每种类型，并考虑嵌套的rate值。

guard let responseJSON = try? JSONSerialization.jsonObject(with: data) as? [String:Any],
      let info = responseJSON["info"] as? [String:Any],
      let rate = info["rate"] as? Double,
      let result = responseJSON["result"] as? Double else {
          return callback(false, nil)
}
let conversionResult = ConversionResult(exchangeRate: rate, exchangeResult: result)
callback(true, conversionResult)

或使用 JSONDecoder ，然后您必须创建结构，只有在根目录中的所有所有值时，才能解码为[String:Double]对象是Double，显然不是这种情况。

struct Root: Decodable {
    let info: Info
    let result: Double
}

struct Info: Decodable {
    let rate: Double
}

guard let responseJSON = try? JSONDecoder().decode(Root.self, from: data) else {
    return callback(false, nil)
}
let conversionResult = ConversionResult(exchangeRate: responseJSON.info.rate, exchangeResult: responseJSON.result)
callback(true, conversionResult)

该代码仅是保持语法的示例。实际上，强烈建议您在解码JSON时不要使用try?。始终catch并处理错误

do {
    let responseJSON = try JSONDecoder().decode(Root.self, from: data)
    let conversionResult = ConversionResult(exchangeRate: responseJSON.info.rate, exchangeResult: responseJSON.result)
   callback(true, conversionResult)
} catch {
    print(error)
    return callback(false, nil)
}

如何进行正确的API调用？

2 个答案: