输入多个单词时，Swift UIText 字段抛出 nil 错误

Question

我的程序正在使用 map ，我有一个 UITextField，用户可以在其中输入搜索短语，然后 map 将在 map 上显示搜索结果的注释。该程序在模拟器中运行良好，但在我的手机上测试时，如果我输入两个作品(如“dog park”)，它会抛出“nil while unwrapping an Optional value”错误。但是如果我只输入“狗”，程序不会在我的手机上抛出错误。我在 ViewDidLoad 中设置了委托(delegate)，并且我的所有网点都已正确链接。我在这里搜索并尝试解决问题无济于事，所以我想我会问问你们是否注意到我遗漏了什么。

这是 UITextLabel 搜索的函数:

@IBAction func searchField(_ sender: UITextField) {
    let allAnnotations = self.mapView.annotations
    self.mapView.removeAnnotations(allAnnotations)
    let request = MKLocalSearchRequest()
    request.naturalLanguageQuery = textField.text!
    request.region = mapView.region

    let search = MKLocalSearch(request: request)
    search.start(completionHandler: {(response, error) in

        if error != nil{
            print("Error occured in search: \(error!.localizedDescription)")
        }else if response!.mapItems.count == 0{
            self.textField.text = "No matches found"
        }else{
            print("Matches found")
            for item in response!.mapItems{
                let annotation = MKPointAnnotation()
                annotation.coordinate = item.placemark.coordinate
                annotation.title = item.name
                annotation.subtitle = item.placemark.thoroughfare! + ", " + item.placemark.locality! + ", " + item.placemark.administrativeArea!
                self.mapView.addAnnotation(annotation)
            }
        }
    })
    sender.resignFirstResponder()
}

Answer 1

所以在进一步研究之后，我发现了一个不需要添加到 naturalLanguageQuery 字符串的答案。问题是 for 循环返回了一个空值。让一名 guard 进来响应解决了这个问题。

@IBAction func searchField(_ sender: UITextField) {
    let allAnnotations = self.mapView.annotations
    self.mapView.removeAnnotations(allAnnotations)
    let request = MKLocalSearchRequest()
    request.naturalLanguageQuery = textField.text!
    request.region = mapView.region

    let search = MKLocalSearch(request: request)
    search.start(completionHandler: {(response, error) in

        if error != nil{
            print("Error occured in search: \(error!.localizedDescription)")
        }else if response!.mapItems.count == 0{
            self.textField.text = "No matches found"
        }else{
            print("Matches found")
            guard let response = response?.mapItems else { return }
            for item in response{
                let annotation = MKPointAnnotation()
                annotation.coordinate = item.placemark.coordinate
                annotation.title = item.name
                annotation.subtitle = item.placemark.thoroughfare! + ", " + item.placemark.locality! + ", " + item.placemark.administrativeArea!

                self.mapView.addAnnotation(annotation)
            }
        }
    })
    sender.resignFirstResponder()
}