Question

目前我正在尝试从JSON数据返回值，但遇到的问题是其中一个值返回null，从而导致我的应用程序崩溃。

这就是json的样子：

  "results": [
    {
      "genre_ids": [
        99
      ],
      "id": 440108,
      "poster_path": null, //The value that's causing incredible headaches!
    },
    {

      "genre_ids": [
        99,
        10402
      ],
      "id": 391698,
      "poster_path": "/uv7syi4vRyjvWoB8qExbqnbuCu5.jpg",//The value trying to get!
    },

]

我正在使用json对象映射器Gloss，这对于这一点已经很好了。以下是我设置对象的方法：

public struct ResultsGenrePosters: Decodable {

  public let results :  [GenrePosters]?

  public init?(json: JSON) {
    results = "results" <~~ json
  }
}

public struct GenrePosters: Decodable, Equatable{

  public let poster : String

  public init? (json: JSON) {

    guard let poster: String = "poster_path" <~~ json
      else {return nil}
    self.poster = poster
  }
  public static func ==(lhs: GenrePosters, rhs: GenrePosters) -> Bool {
    return lhs.poster == rhs.poster
  }


  static func updateGenrePoster(genreID: NSNumber, urlExtension: String, completionHandler:@escaping (_ details: [String]) -> Void){

    let nm = NetworkManager.sharedManager

    nm.getJSONData(type:"genre/\(genreID)", urlExtension: urlExtension, completion: {
      data in

      if let jsonDictionary = nm.parseJSONData(data)
      {
        guard let genrePosters = ResultsGenrePosters(json: jsonDictionary)

          else {
            print("Error initializing object")
            return
        }

        guard let posters = genrePosters.results

          else {
            print("No poster exists for genre: \(genreID)")// This keeps on triggering when the null object is hit, this is where it would be good to move to the next array to get that value
            return
        }

        let postersArray = posters.map {$0.poster}// converts custom object "GenrePosters" to String(poster value)
        completionHandler(postersArray)
      }
    })
  }
}

Answer 1

    guard let poster: String = "poster_path" <~~ json

应该是

guard let poster = ("poster_path" <~~ json) as? String

（当然你使用的是我一无所知的库，所以库可能会崩溃.JSONSerialization是你的朋友。它的工作原理。每个人都知道它的作用）。

Answer 2

    for data in results as! [Dictionary<String,AnyObjects>]{
    var value1 = data["key"] as? String
    if value1 == nil{value1 = ""}else{}
    }
    }
    That was just a simple logic but completely work for me all the time. :)

如果json数组中的值返回null，如何返回下一个非null的json值？

2 个答案: