在Swift中解析json,AnyObject类型

我试图解析一个json，但我有一些困难的数据类型，特别是AnyObject类型downcasting。

让我们考虑下面的json(它是一个完整的json的提取)。

{  "weather":
   [
      {
         "id":804,"main":"Clouds","description":"overcast clouds","icon":"04d"
      }
   ],}

对我来说，json可以描述如下：

- json: Dictionary of type [String: AnyObject] (or NSDictionary,so = [NSObject,AnyObject] in Xcode 6 b3)
    - "weather": Array of type [AnyObject] (or NSArray)
         - Dictionary of type [String: AnyObject] (or NSDictionary,AnyObject] in Xcode 6 b3)

我的json是AnyObject类型的！ (我使用JSONObjectWithData从URL获取JSON)。

然后我想访问天气词典。这里是我写的代码。

var localError: NSError?
var json: AnyObject! = NSJSONSerialization.JSONObjectWithData(data,options: NSJSONReadingOptions.MutableContainers,error: &localError)

if let dict = json as? [String: AnyObject] {
 if let weatherDictionary = dict["weather"] as? [AnyObject] {
      // Do stuff with the weatherDictionary
    }
}

这是我得到的错误

Playground execution Failed: error: <EXPR>:28:56: error: '[AnyObject]' is not a subtype of '(String,AnyObject)'
        if let weatherDictionary = dict["weather"] as? [AnyObject] {

我不明白为什么dict [“weather”]与(String，AnyObject)的子类型比较而不是AnyObject。

我声明我的字典为[String：AnyObject]，所以我使用String键访问一个值，我应该有一个AnyObject，没有？

如果我使用NSDictionary而不是[String：AnyObject]，它的工作原理。

如果我使用NSArray而不是[AnyObject]，它的工作原理。

- The Xcode 6 beta 3 release notes tell that "NSDictionary* is now imported from Objective-C APIs as [NSObject : AnyObject].".
- And the Swift book: "When you bridge from an NSArray object to a Swift array,the resulting array is of type [AnyObject]."

编辑

我忘了强行解开dict [“天气”]！

if let dict = json as? [String: AnyObject] {
    println(dict)
       if let weatherDictionary = dict["weather"]! as? [AnyObject] {
            println("\nWeather dictionary:\n\n\(weatherDictionary)")
            if let descriptionString = weatherDictionary[0]["description"]! as? String {
                println("\nDescription of the weather is: \(descriptionString)")
        }
    }
}

注意，我们应该仔细检查第一个Optional的存在。

if let dict = json as? [String: AnyObject] {
    for key in ["weather","traffic"] {
        if let dictValue = dict[key] {
            if let subArray = dictValue as? [AnyObject] {
                println(subArray[0])
            }
        } else {
            println("Key '\(key)' not found")
        }
    }
}

这对我在操场和终端使用env xcrun swift工作得很好

UPDATED FOR SWIFT 3.0

我更新了Swift 3的代码，还展示了如何将解析的JSON包装到对象中。感谢所有的投票！

import Foundation

struct Weather {
    let id: Int
    let main: String
    let description: String
    let icon: String
}

extension Weather {
    init?(json: [String: Any]) {
        guard
            let id = json["id"] as? Int,let main = json["main"] as? String,let description = json["description"] as? String,let icon = json["icon"] as? String
        else { return nil }
        self.id = id
        self.main = main
        self.description = description
        self.icon = icon
    }
}

var jsonStr = "{\"weather\":[{\"id\":804,\"main\":\"Clouds\",\"description\":\"overcast clouds\",\"icon\":\"04d\"}],}"

enum JSONParseError: Error {
    case notADictionary
    case missingWeatherObjects
}

var data = jsonStr.data(using: String.Encoding.ascii,allowLossyConversion: false)
do {
    var json = try JSONSerialization.jsonObject(with: data!,options: [])
    guard let dict = json as? [String: Any] else { throw JSONParseError.notADictionary }
    guard let weatherJSON = dict["weather"] as? [[String: Any]] else { throw JSONParseError.missingWeatherObjects }
    let weather = weatherJSON.flatMap(Weather.init)
    print(weather)
}
catch {
    print(error)
}

– 上一个答案 –

import Foundation

var jsonStr = "{\"weather\":[{\"id\":804,}"
var data = jsonStr.dataUsingEncoding(NSASCIIStringEncoding,allowLossyConversion: false)
var localError: NSError?
var json: AnyObject! = NSJSONSerialization.JSONObjectWithData(data!,error: &localError)

if let dict = json as? [String: AnyObject] {
    if let weather = dict["weather"] as? [AnyObject] {
        for dict2 in weather {
            let id = dict2["id"]
            let main = dict2["main"]
            let description = dict2["description"]
            println(id)
            println(main)
            println(description)
        }
    }
}

因为我仍然拿起来投票的这个答案，我想我会重新审视它的Swift 2.0：

import Foundation

var jsonStr = "{\"weather\":[{\"id\":804,allowLossyConversion: false)
do {
    var json = try NSJSONSerialization.JSONObjectWithData(data!,options: NSJSONReadingOptions.MutableContainers)

    if let dict = json as? [String: AnyObject] {
        if let weather = dict["weather"] as? [AnyObject] {
            for dict2 in weather {
                let id = dict2["id"] as? Int
                let main = dict2["main"] as? String
                let description = dict2["description"] as? String
                print(id)
                print(main)
                print(description)
            }
        }
    }

}
catch {
    print(error)
}

最大的区别是变量json不再是可选类型和do / try / catch语法。我也去了键入id，main和description。

原文链接：https://www.f2er.com/swift/321055.html

在Swift中解析json,AnyObject类型

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