Swift：无法使用 NSObjects 将“NSNull”类型的值转换为“NSDictionary”答案

【问题标题】：Swift: Could not cast value of type 'NSNull' to 'NSDictionary' using NSObjectsSwift：无法使用 NSObjects 将“NSNull”类型的值转换为“NSDictionary”
【发布时间】：2016-02-01 00:55:06
【问题描述】：

Swift 2.1 Xcode 7.1 Alamofire 2.0.2

使用我在下面描述的 Alamofire 函数，我正在从 API 中以 JSON 格式检索传单列表：

Alamofire.request(Router.GetList()).responseJSON { (_, _, result) in
      var flyers = [Flyer]()

      switch result {
        case .Success(let json):
          if let responseObject = json as? [String: AnyObject], let hits = responseObject["hits"] as? [[String: AnyObject]] {
print(hits)
            for dictionary in hits {
              flyers.append(Flyer(dictionary: dictionary))
            }

            completionHandler(flyers, nil)
          }
        case .Failure(_, let error):
          completionHandler(nil, error as NSError)
      }
    }

print(hits) 的 JSON 响应结果是：

[["title": Code 103, 
 "event": {
    "_id" = 54b0561f274441073751;
    name = "Code 103";
    }
],
["title": Code 104, 
 "event": {
    "_id" = 54b0561f274441073752;
    name = "Code 104";
    }
]]

如下所示，Flyer 类有一个属性（“事件”），它引用了 Event 类的两个属性，id and name：

class Flyer: NSObject{

  var title: String?
  var event: Event?

  init(dictionary: [String: AnyObject]) {
    title    = dictionary["title"] as? String
    event    = Event(dictionary: dictionary["event"] as! [String: AnyObject])
  }
}

class Event: NSObject{

  var id: String?
  var name: String?

  init(dictionary: [String: AnyObject]){

    id              = dictionary["id"] as? String
    name            = dictionary["name"] as? String
  }
}

我收到下一个错误：

Could not cast value of type 'NSNull' (0x107d50378) to 'NSDictionary' (0x107d4fd60).

这个错误位于Flyer类中的一行：

event    = Event(dictionary: dictionary["event"] as! [String: AnyObject])

而且我不知道我能做些什么来解决这个问题，因为响应不为空。感谢帮助

【问题讨论】：

看来event 键的值可以是nil，它由NSNull 对象表示。过滤这些案例并相应地处理它们。

标签： ios json swift alamofire

【解决方案1】：

以下内容在操场上完美运行：尝试清理并重建。

let json: AnyObject = [
    "hits": [
        [
            "title": "Code 103",
            "event": [
            "_id": "54b0561f274441073751",
            "name": "Code 103"
            ]
        ],
        [
            "title": "Code 104",
            "event": [
                "_id": "54b0561f274441073752",
                "name": "Code 104"
            ]
        ]
    ]
]

class Flyer: NSObject{

    var title: String?
    var event: Event?

    init(dictionary: [String: AnyObject]) {
        title = dictionary["title"] as? String
        event = Event(dictionary: dictionary["event"] as! [String: AnyObject])
    }
}

class Event: NSObject{

    var id: String?
    var name: String?

    init(dictionary: [String: AnyObject]){

        id = dictionary["id"] as? String
        name = dictionary["name"] as? String
    }
}

var flyers = [Flyer]()

if let responseObject = json as? [String: AnyObject], let hits = responseObject["hits"] as? [[String: AnyObject]] {
    print(hits)
    for dictionary in hits {
        flyers.append(Flyer(dictionary: dictionary))
    }
}

【讨论】：