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