swift - 无法检查模型是否符合 Swift 协议(protocol)

Question

我有协议(protocol):

protocol SelectingRowProtocol : class {

    func selectItemAtIndexPath(row: Int)
}

和模型:

class HRVacanciesViewModel :  BaseModel, CDTableAdapterViewModel, SelectingRowProtocol {


weak var selectingRowDelegate : SelectingRowProtocol?

/* Selecting */

func selectItemAtIndexPath(row: Int) {
  print("selected")
}

但是当我尝试检查时，如果模型符合协议(protocol)，它评估为 false:

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

    if let model = self.viewModel as? SelectingRowProtocol {
        //currentVC responds to the MyCustomProtocol protocol =]
    }
}

为什么会这样？

Answer 1

You can try making the protocol method as optional in order to avoid forced wrapping

@objc protocol SelectingRowProtocol : class {
  optional func selectItemAtIndexPath(row: Int)
}

And you can check if your viewmodel conforms to protocol like this:-

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
  if self.viewModel is SelectingRowProtocol { //Should returns true
    //currentVC responds to the MyCustomProtocol protocol =]
//now call like this
(self.viewModel as? SelectingRowProtocol)?.selectItemAtIndexPath?(row: indexPath.row)
  }
}