swift - 无法使用 ViewModel 加载数据

Question

• tableView 数据源已在 IB 中正确设置
• viewController 身份也在 IB 中正确设置

这是我的viewModel

class StatusCodeViewModel {

    let apiClient = APIClient.shared
    var statusCodes: [StatusCode] = []
    let identifier = "statusCodeCell"

    init() {}


    func loadStatusCodes() {
        apiClient.execute(service: .statusCode) { statusCodes in
            self.statusCodes = statusCodes
        }
    }

}

以及我想要加载数据的viewController

class ViewController: UIViewController {

    @IBOutlet weak var tableView: UITableView!
    var viewModel: StatusCodeViewModel? {
        didSet {
            if viewModel!.statusCodes.count > 0 {
                self.tableView.reloadData()
            }
        }
    }


    override func viewDidLoad() {
        super.viewDidLoad()
        viewModel = StatusCodeViewModel()
        viewModel!.loadStatusCodes()
    }
}

extension ViewController : UITableViewDataSource {
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        if let statusCodes = viewModel!.statusCodes as? [StatusCode] {
            return statusCodes.count
        }
        return 0
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: viewModel!.identifier)
        cell?.textLabel!.text = viewModel!.statusCodes[indexPath.row].title
        return cell!
    }


}

数据计数为0，tableView中没有显示数据

Answer 1

您已经设置了 View 模型，这将在初始化时发生。

当 api 返回调用时，您必须实现某种回调 - 最简单的方法是协议(protocol)。

protocol StatusCodeViewModelDelegate {
    func callFinished()
}

class StatusCodeViewModel {

    let apiClient = APIClient.shared
    var statusCodes: [StatusCode] = []
    let identifier = "statusCodeCell"
    var delegate : StatusCodeViewModelDelegate?

    init() {}


    func loadStatusCodes() {
        apiClient.execute(service: .statusCode) { statusCodes in
            self.statusCodes = statusCodes
            delegate?.callFinished()
        }
    }

}

然后在你的viewController中:

override func viewDidLoad() {
    super.viewDidLoad()
    viewModel = StatusCodeViewModel()
    viewModel.delegate = self
    viewModel!.loadStatusCodes()
}

func callFinished() {
    self.tableView.reloadData()
}

不要忘记延长您刚刚创建的委托(delegate):

class ViewController: UIViewController, StatusCodeViewModelDelegate {

或者，正如 @rmaddy 建议的那样，在 View 模型中将 loadStatusCodes 更改为:

func loadStatusCodes(completion: @escaping () -> Void) {
    apiClient.execute(service: .statusCode) { statusCodes in
        self.statusCodes = statusCodes
    }
}

然后，在viewDidLoad中:

override func viewDidLoad() {
    super.viewDidLoad()
    viewModel = StatusCodeViewModel()
    viewModel!.loadStatusCodes {
        self.tableView.reloadData()
    }
}