Question

我有一个名为 Track 的模型。它具有一组基本属性和一组扩展属性。轨道列表及其基本属性是通过 search API调用获取的，然后我需要使用这些轨道ID 进行另一个API调用，以获取其扩展属性。

问题是如何最好地组合两个API调用的结果，并将扩展属性填充到已创建的 Track 对象中，当然还要通过ID将它们匹配（不幸的是，这两个调用的结果中的属性名称都不相同）。请注意，实际结果集中还会返回更多键-两个调用中的每个调用都具有约20-30个属性。

Track.swift

struct Track: Decodable {

// MARK: - Basic properties

let id: Int
let title: String

// MARK: - Extended properties

let playbackURL: String

enum CodingKeys: String, CodingKey {
    case id = "id"

    case title = "title"

    case playbackUrl = "playbackUrl"
}

init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)

    let idString = try container.decode(String.self, forKey: CodingKeys.id)
    id = idString.int ?? 0

    title = try container.decode(String.self, forKey: CodingKeys.title)

    playbackURL = try container.decodeIfPresent(String.self, forKey: CodingKeys.playbackUrl) ?? ""
}
}

ViewModel.swift

let disposeBag = DisposeBag()
var searchText = BehaviorRelay(value: "")
private let provider = MoyaProvider<MyAPI>()
let jsonResponseKeyPath = "results"

public lazy var data: Driver<[Track]> = getData()

private func searchTracks(query: String) -> Observable<[Track]> {
    let decoder = JSONDecoder()
    return provider.rx.request(.search(query: query))
        .filterSuccessfulStatusCodes()
        .map([Track].self, atKeyPath: jsonResponseKeyPath, using: decoder, failsOnEmptyData: false)
        .asObservable()
}

private func getTracksMetadata(tracks: Array<Track>) -> Observable<[Track]> {
    let trackIds: String = tracks.map( { $0.id.description } ).joined(separator: ",")
    let decoder = JSONDecoder()
    return provider.rx.request(.getTracksMetadata(trackIds: trackIds))
        .filterSuccessfulStatusCodes()
        .map({ result -> [Track] in

        })
        .asObservable()
}

private func getData() -> Driver<[Track]> {
    return self.searchText.asObservable()
        .throttle(0.3, scheduler: MainScheduler.instance)
        .distinctUntilChanged()
        .flatMapLatest(searchTracks)
        .flatMapLatest(getTracksMetadata)
        .asDriver(onErrorJustReturn: [])
}

.search API调用的JSON结果的结构如下：

{
  "results": [
    {
      "id": "4912",
      "trackid": 4912,
      "artistid": 1,
      "title": "Hello babe",
      "artistname": "Some artist name",
      "albumtitle": "The Best Of 1990-2000",
      "duration": 113
    },
    { 
      ...
    }
  ]
}

.getTracksMetadata API调用的JSON结果的结构如下：

[
  {
    "TrackID": "4912",
    "Title": "Hello babe",
    "Album": "The Best Of 1990-2000",
    "Artists": [
      {
        "ArtistID": "1",
        "ArtistName": "Some artist name"
      }
    ],
    "SomeOtherImportantMetadata1": "Something something 1",
    "SomeOtherImportantMetadata2": "Something something 2",
    "SomeOtherImportantMetadata3": "Something something 3"
  },
  { 
    ...
  }
]

Answer 1

这里的解决方案是两阶段方法。首先，您应该为两个网络调用定义两个不同的结构，为合并的结果定义第三个结构。假设您选择：

struct TrackBasic {
    let id: Int 
    let title: String 
}

struct TrackMetadata {
    let id: Int // or whatever it's called.
    let playbackURL: String
}

struct Track {
    let id: Int 
    let title: String 
    let playbackURL: String
}

并这样定义函数：

func searchTracks(query: String) -> Observable<[TrackBasic]>
func getTracksMetadata(tracks: [Int]) -> Observable<[TrackMetadata]>

现在您可以进行两次调用，并将来自两个单独端点的数据包装到组合的结构中：

searchText
    .flatMapLatest { searchTracks(query: $0) }
    .flatMapLatest { basicTracks in
        Observable.combineLatest(Observable.just(basicTracks), getTracksMetadata(tracks: basicTracks.map { $0.id }))
    }
    .map { zip($0.0, $0.1) }
    .map { $0.map { Track(id: $0.0.id, title: $0.0.title, playbackURL: $0.1.playbackURL) } }

以上假设轨道元数据的顺序与请求时的顺序相同。如果不是这种情况，则最后一个地图将必须更复杂。

使用RxSwift

1 个答案: