在Swift中正确解析JSON 3

我试图获取一个JSON响应，并将结果存储在一个变量。我有这个代码的版本工作在以前的版本的Swift，直到GM版本的Xcode 8发布。我看了几个类似的帖子在StackOverflow： Swift 2 Parsing JSON – Cannot subscript a value of type ‘AnyObject’和 JSON Parsing in Swift 3。

然而，似乎在那里传达的想法不适用于这种情况。

如何正确解析Swift 3中的JSON响应？
在Swift 3中读取JSON的方式有什么变化？

下面是有问题的代码(它可以在操场上运行)：

import Cocoa
 
let url = "https://api.forecast.io/forecast/apiKey/37.5673776,122.048951"
 
if let url = NSURL(string: url) {
    if let data = try? Data(contentsOf: url as URL) {
        do {
            let parsedData = try JSONSerialization.jsonObject(with: data as Data,options: .allowFragments)
 
        //Store response in NSDictionary for easy access
        let dict = parsedData as? NSDictionary
 
        let currentConditions = "\(dict!["currently"]!)"
 
        //This produces an error,Type 'Any' has no subscript members
        let currentTemperatureF = ("\(dict!["currently"]!["temperature"]!!)" as NSString).doubleValue
 
            //Display all current conditions from API
            print(currentConditions)
 
            //Output the current temperature in Fahrenheit
            print(currentTemperatureF)
 
        }
        //else throw an error detailing what went wrong
        catch let error as NSError {
            print("Details of JSON parsing error:\n \(error)")
        }
    }
}

编辑：以下是打印后的API调用的结果示例(currentConditions)

["icon": partly-cloudy-night,"precipProbability": 0,"pressure": 1015.39,"humidity": 0.75,"precipIntensity": 0,"windSpeed": 6.04,"summary": Partly Cloudy,"ozone": 321.13,"temperature": 49.45,"dewPoint": 41.75,"apparentTemperature": 47,"windBearing": 332,"cloudCover": 0.28,"time": 1480846460]

首先，不要从远程URL同步加载数据，请使用像URLSession这样的异步方法。

‘Any’ has no subscript members

发生因为编译器不知道中间对象是什么类型的(例如当前在[“当前”]！[“温度”])，并且由于您使用的是NSDictionary类的Foundation集合类型，编译器根本不知道类型。

此外，在Swift 3中，需要通知编译器有关所有下标对象的类型。

您必须将JSON序列化的结果转换为实际类型。

此代码使用URLSession和独有的Swift本机类型

let urlString = "https://api.forecast.io/forecast/apiKey/37.5673776,122.048951"
 
let url = URL(string: urlString)
URLSession.shared.dataTask(with:url!) { (data,response,error) in
  if error != nil {
    print(error)
  } else {
    do {
 
      let parsedData = try JSONSerialization.jsonObject(with: data!,options: []) as! [String:Any]
      let currentConditions = parsedData["currently"] as! [String:Any]
 
      print(currentConditions)
 
      let currentTemperatureF = currentConditions["temperature"] as! Double
      print(currentTemperatureF)
    } catch let error as NSError {
      print(error)
    }
  }
 
}.resume()

要打印所有可以写入的currentConditions的键/值对

let currentConditions = parsedData["currently"] as! [String:Any]
 
  for (key,value) in currentConditions {
    print("\(key) - \(value) ")
  }

编辑：

苹果在Swift博客中发表了一篇综合文章：Working with JSON in Swift

在Swift中正确解析JSON 3

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