Swift MVVM 装箱绑定

Question

我只是想用 WeatherViewController 创建一个天气应用程序，显示带有 cells 的 tableView ]，当单元格被点击时导致WeatherDetailsViewController。

我正在使用 boxing 方式进行 binding 如果我设置 Dynamic type[=56 我会感到困惑=] 在下面示例中的 model 和 viewModel 中。你会明白我的意思。

这就是拳击Class

    class Dynamic<T>: Decodable where T: Decodable {

    typealias Listener = (T) -> ()
    var listener: Listener?

    var value: T {
        didSet {
            listener?(value)
        }
    }

    func bind(listener: @escaping Listener) {
        self.listener = listener
        self.listener?(self.value)
    }

    init(_ value: T) {
        self.value = value
    }

    private enum CodingKeys: CodingKey {
        case value
    }
}

这是天气模型结构

struct Weather: Decodable {

    let date: Dynamic<Int>
    let description: Dynamic<String>
    let maxTemperature: Dynamic<Double>

    private enum CodingKeys: String, CodingKey  {
        case date = "time"
        case description = "summary"
        case maxTemperature = "temperatureMax"
    }

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        date = try Dynamic(container.decode(Int.self, forKey: .date))
        description = try Dynamic(container.decode(String.self, forKey: .description))
        maxTemperature = try Dynamic(container.decode(Double.self, forKey: .maxTemperature))
    }

}

这是我的 WeatherListViewModel 和 WeatherViewModel

在我的 WeatherViewModel 中，我已将类型指定为 Dynamic，但也在模型中指定了类型以便绑定到我的 WeatherDetailsViewController，对吗？

class WeatherListViewModel {

    var weatherViewModels: [WeatherViewModel]
    private var sessionProvider: URLSessionProvider

    init(sessionProvider: URLSessionProvider) {
        self.sessionProvider = sessionProvider
        self.weatherViewModels = [WeatherViewModel]()
    }

    func numberOfRows(inSection section: Int) -> Int {
        return weatherViewModels.count
    }

    func modelAt(_ index: Int) -> WeatherViewModel {
        return weatherViewModels[index]
    }

    func didSelect(at indexPath: Int) -> WeatherViewModel {
        return weatherViewModels[indexPath]
    }

}

这是用于网络获取的 WeatherListViewModel 扩展，我在其中初始化 WeatherViewModel

func fetchWeatherLocation(withLatitude latitude: CLLocationDegrees, longitude: CLLocationDegrees, completion: @escaping handler) {
    sessionProvider.request(type: WeatherWrapper.self, service: WeatherService.specificLocation, latitude: latitude, longitude: longitude) { [weak self] result in
        switch result {
        case let .success(weatherWrapper):
            let weathers = weatherWrapper.daily.weathers

            self?.weatherViewModels = weathers.map {
                return WeatherViewModel(weather: [=14=])
            }
            completion()
        case let .failure(error):
            print("Error: \(error)")
        }
    }
}

这是 WeatherViewModel
结构 WeatherViewModel {

    private(set) var weather: Weather

    var temperature: Dynamic<Double>
    var date: Dynamic<Int>
    var description: Dynamic<String>

    init(weather: Weather) {
        self.weather = weather
        self.temperature = Dynamic(weather.maxTemperature)
        self.date = Dynamic(weather.date)
        self.description = Dynamic(weather.description)
    }

}

这是我的 WeatherDetailsViewController 这里我分别给labels赋值绑定得到变化

class WeatherDetailsViewController: UIViewController {

    @IBOutlet private var imageView: UIImageView!

    @IBOutlet private var cityLabel: UILabel!
    @IBOutlet private var dateLabel: UILabel!
    @IBOutlet private var descriptionLabel: UILabel!
    @IBOutlet private var temperatureLabel: UILabel!

    var viewModel: WeatherViewModel?

    override func viewDidLoad() {
        super.viewDidLoad()

        setupVMBinding()
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        navigationItem.largeTitleDisplayMode = .never
    }

    private func setupVMBinding() {
        if let viewModel = viewModel {
            viewModel.date.bind {
                self.dateLabel.text = [=16=].toString()
            }

            viewModel.temperature.bind {
                self.temperatureLabel.text = "\([=16=])"
            }

            viewModel.description.bind {
                self.descriptionLabel.text = [=16=].description
            }
        }
    }

}

问题是，我是否只是在模型和视图模型中重复编写 Dynamic 类型？有没有更好的方法来做到这一点，或者我在正确的轨道上。抱歉，代码示例很长。

Answer 1

我认为您在 Weather 模型中重复编写 Dynamic。

不需要是Dynamic类型。

您可以创建一个 GenericDataSource

class GenericDataSource<T>: NSObject {
    var data: Dynamic<T>?  
}

在您的视图模型中。这将引用您的天气模型而无需创建动态类型。

class WeatherViewModel {
    var dataSource: GenericDataSource<Weather>?

    ....
}

在你的视图控制器中

class WeatherDetailsViewController {

    var viewModel: WeatherViewModel?

    override func viewDidLoad() {
       viewModel = ViewModel()

       var dataSource = GenericDataSource<Weather>()
       dataSource.data = Dynamic(Weather)

       viewModel.dataSource = dataSource

       setupVMBinding()
    }

    private func setupVMBinding() {
        viewModel?.dataSource?.data?.bind {
            self.dateLabel.text = [=12=].date
            self.temperatureLabel.text = "\([=12=].maxTemperature)"
            self.descriptionLabel.text = [=12=].description
        }
    }
}