绑定UITextField以查看模型变量

Question

我正在尝试使用Bond将UI元素绑定到我的视图模型。当我试图将信号绑定到我的视图模型searchString时，Xcode8.3.3给我一个“错误的参数标签in call (have ' to :'，expected 'signal:')”错误。怎么啦？

import UIKit
import Bond
import ReactiveKit

class SearchViewModel {
   let searchString = Observable<String>("")
}

class SearchViewController: UIViewController {

   @IBOutlet weak var searchTextField: UITextField!

   let viewModel = SearchViewModel()

   override func viewDidLoad() {
      super.viewDidLoad()
      bindToViewModel()
   }

   func bindToViewModel() {
      searchTextField.reactive.text.bind(to: viewModel.searchString)
   }
}

Answer 1

问题是：

let searchString = Observable<String>("")

需要满足以下条件：

let searchString = Observable<String?>("")

因为UITextField: BindableProtocol { public func bind(signal: Signal<String?, NoError>) -> Disposable { return reactive.text.bind(signal: signal) } }期望一个可选的，就像3stud1ant3指出的那样。