MKPlacemark 上的参数类型错误

Question

我正在尝试在 swift 中编写一个创建 MKMapItem 的函数，但出现了字符串错误。这是代码：

func mapItem() -> MKMapItem {
    let addressDictionary = [String(kABPersonAddressStreetKey): subtitle]
    let placemark = MKPlacemark(coordinate: coordinate, addressDictionary: addressDictionary)

    let mapItem = MKMapItem(placemark: placemark)
    mapItem.name = title

    return mapItem
}

我尝试创建 placemark 时遇到以下错误：

Cannot convert value of type "[String : String?]" to expected argument type "[String : AnyObject]?

完整 class 代码：

class Bar: NSObject, MKAnnotation {

    // MARK: Properties
    let id: Int
    let title: String
    let locationName: String
    let url: String
    let imageUrl: String
    let tags: String
    let coordinate: CLLocationCoordinate2D

    // MARK: Initialisation
    init(id: Int, adress: String, name: String, url: String, tags: String, imageUrl: String, coordinate: CLLocationCoordinate2D) {
        // Affectation des attributs
        self.id = id
        self.title = name
        self.locationName = adress
        self.url = url
        self.imageUrl = imageUrl
        self.tags = tags
        self.coordinate = coordinate
    }

    // MARK: Subtitle

    var subtitle: String {
        return locationName
    }

    // MARK: Helper

    func mapItem() -> MKMapItem {
        var addressDictionary : [String:String]?
        addressDictionary = [String(kABPersonAddressStreetKey): subtitle]

        let placemark = MKPlacemark(coordinate: coordinate, addressDictionary: addressDictionary)

        let mapItem = MKMapItem(placemark: placemark)
        mapItem.name = title

        return mapItem
    }    
}

Answer 1

您的副标题属性看起来像一个可选的字符串，但是 MKPlacemark 初始值设定项需要 [String : AnyObject]? 类型的参数用于 addressDictionary。

这是什么意思？

预期的参数类型是一个字典，其中键是 String，值是 AnyObject，所以它可以是任何东西。除了零值之外的任何东西！但是你的 subtitle 属性可能是零，所以你有这个错误。

在使用之前解开你的价值：

func mapItem() -> MKMapItem {

    var addressDictionary : [String:String]?

    if let subtitle = subtitle {
        // The subtitle value used here is a String,
        // so addressDictionary conforms to its [String:String] type
        addressDictionary = [String(kABPersonAddressStreetKey): subtitle
    }

    let placemark = MKPlacemark(coordinate: coordinate, addressDictionary: addressDictionary)

    let mapItem = MKMapItem(placemark: placemark)
    mapItem.name = title
    return mapItem
}

如果 subtitle 为零，您还可以 return 一个可选的 MKMapItem objects。选择权在你；)

Answer 2

替换此字符串：

  let title: String?

替换此代码：

 var subtitle: String? {
        return locationName
    }

您需要将字幕转换为 AnyObject，如下所示：

let addressDict = [String(kABPersonAddressStreetKey): self.subtitle as! AnyObject]

"func mapItem() -> MKMapItem { }" 的完整代码将是：

func mapItem() -> MKMapItem {
    let addressDict = [String(kABPersonAddressStreetKey): self.subtitle as! AnyObject]
    let placemark = MKPlacemark(coordinate: self.coordinate, addressDictionary: addressDict)

    let mapItem = MKMapItem(placemark: placemark)
    mapItem.name = self.title

    return mapItem
  }

MKPlacemark 上的参数类型错误

Argument type error on MKPlacemark

ios

swift

mkplacemark