类型“ customDataObject”不符合协议“序列”

Question

What I'm trying to do is retrieve json data(which is in array format) and check to see if my local array already contains the data, if it does move on to the next value in the JSON data until their is a value that the array doesn't contain then append it to the array. This data in the array must be in order. I'm attempting to do this now but get the error:

Type 'ResultsGenrePosters' does not conform to protocol 'Sequence'

This is what it looks like:

public struct ResultsGenrePosters: Decodable {

  public let results :  [GenrePosters]?

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


public struct GenrePosters: Decodable {

  public let poster : String

  public init? (json: JSON) {

    guard let poster: String = "poster_path" <~~ json
    else {return nil}
  self.poster = poster
  }

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

    var posterArray: [String] = []

    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 posterString = genrePosters.results?[0].poster

          else {
            print("No such item")
            return
        }

        for posterString in genrePosters {

          if posterArray.contains(posterString){continue
          } else { posterArray.append(posterString) } //This is where the error happens

        }
      }
      completionHandler(posterArray)
    })
  }

}

Answer 1

Alt + click on genrePosters and what does it tell you? It should say its ResultsGenrePosters because thats what the error is saying. Now look at the type of posterArray; its an array of String, not Array ResultsGenrePosters. I think you mean to write for poster in genrePosters and have confused yourself about the types because you wrote for posterString in genrePosters .

Maybe you want to use map to transform genrePosters into a [String] ?

This transforms your posterArray, if it exists into an array containing just the poster names. If it doesn't exist you get an empty array. This only works if poster is String. If its String? you should use flatMap instead.

let posterNames = genrePosters.results?.map { $0.poster } ?? [String]()