ios - RAC MutableProperty Producer 不向订阅者发送事件

Question

我正在使用 RAC4 开发一个应用程序，它从服务器获取城市对象列表并将它们作为 JSON 返回。我通过将每个城市及其适当的属性存储为 City 对象来处理响应。然后，我将每个城市映射到 CityViewModel 类型，并将 [CityViewModel] 类型的数组存储为 MutableProperty。从这里每个城市都被归档到一个 tableViewCell 中，并在单元格中使用名称和下载进度条显示。点击时，单元会触发另一个服务器请求，使用城市 nid(城市 ID)作为参数来下载包含图像等的大型 .zip 文件。

此处的目标是通过进度的实时更新为进度条设置动画。点击时，单元格调用 downloadCityData(nid: Int)启动一切的功能。

问题是，在更新城市属性的同时，城市 MutableProperty<[CityViewModel]>在 DataViewModel 之外没有通知它的听众任何变化目的。 (在这种情况下是 DetailViewController )

View Controller :

class DetailViewController: UIViewController {

    @IBOutlet weak var cityTableView: UITableView!

    private var bindingHelper: TableViewBindingHelper<CityViewModel>!

    var viewModel: DetailViewModel?

    override func viewDidLoad() {

        super.viewDidLoad()
        self.viewModel = DetailViewModel()
        self.viewModel!.cities.producer
            .startOn(UIScheduler())
            .startWithNext{ x in
                /// this doesn't hear any changes as progress updates
            }


        bindingHelper = TableViewBindingHelper(tableView: cityTableView, sourceSignal: self.viewModel!.cities.producer, nibName: "CityCell")

    }
}

View 模型:

class DetailViewModel: NSObject {

    var dataManager: DataManager

    let cities = MutableProperty<[CityViewModel]>([CityViewModel]())

    override init() {

        self.dataManager = DataManager()
        super.init()

        self.dataManager.progressMarker.producer
            .observeOn(UIScheduler())
            .startWithNext{ [weak self] (nid, progress) in
                self!.cities.value = (self!.cities.value.map{ city in
                    if city.nid.value == nid {
                        print(nid, progress)
                        city.downloading.value = true
                        city.progress.value = progress
                    }
                    return city
                })
        }

    }

    func downloadCityData(nid: Int) -> SignalProducer<(JSON?, Float), NSError> {
        return dataManager.getCityData(nid)
            .on(next: { (json, progress) in
                /// download complete
                print("download complete")
                self.cities.value = (self.cities.value.map{ city in
                    if city.nid.value == nid {
                        city.downloading.value = false
                        city.downloadedBool.value = true
                        city.upToDate.value = true
                    }
                    return city
                    })
            })
    }   
}

数据管理器:

class DataManager: NSObject {

    private let restClient = RestClient()

    let progressMarker = MutableProperty<(Int, Float)>(0, 0)

    override init() {
        super.init()
    }

    func getCityData(nid: Int) -> SignalProducer<(JSON?, Float), NSError> {
        return restClient.fetchCityData(nid)
            .filter{ (fileName, progress) in
                self.progressMarker.value = (nid, progress)
                return fileName.characters.count > 0
            }
            .flatMap(FlattenStrategy.Latest, transform: unzipCityData)
            .flatMap(FlattenStrategy.Latest, transform: unpackCityData)
    }
}

城市景观模型:

class CityViewModel: NSObject {

    private let city: City

    let name: ConstantProperty<String>
    let nid: ConstantProperty<Int>
    let progress: MutableProperty<Float>

    let downloading: MutableProperty<Bool>
    let downloadedBool: MutableProperty<Bool>
    let downloadedString: MutableProperty<String>
    let upToDate: MutableProperty<Bool>

    init(city: City) {

        self.city = city
        name = ConstantProperty(city.name)
        nid = ConstantProperty(city.nid)
        progress = MutableProperty(city.progress)

        downloading = MutableProperty(city.downloading)
        downloadedBool = MutableProperty(city.downloaded)
        downloadedString = MutableProperty(city.downloaded ? "downloaded" : "download now")
        upToDate = MutableProperty(city.upToDate)

        super.init()  
    }  
}

城市:

struct City {

    var name: String
    var nid: Int
    var timestamp: Int
    var progress: Float
    var downloading: Bool
    var downloaded: Bool
    var upToDate: Bool

    init() {
        name = ""
        nid = 0
        timestamp = 0
        progress = 0
        downloading = false
        downloaded = false
        upToDate = false
    }   
}

Answer 1

我看到你正在使用 Colin Eberhardt's TableViewBindingHelper .看起来这正在剥夺 ViewController 监听和观察 viewModel 信号的能力。我之前在使用这个帮助程序类时也遇到过问题。