MKAnnotation - 无法分配给 属性：'title' 是一个 get-only 属性

Question

如何解决这个构建问题 - 我只是想为 mapkit 创建一个注释：

错误："MKAnnotation - Cannot assign to property: 'title' is a get-only property"

import UIKit
import MapKit

class ViewController: UIViewController {

    @IBOutlet weak var mapView: MKMapView!

    override func viewDidLoad() {
        super.viewDidLoad()

        // Annotations
        var annotation:MKAnnotation
        annotation.title = "test"    // ** ISSUE IS HERE **         
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

}

备注： - 已下载最新版本 XCode - 这与 Swift 2.0 有关吗？ -

Answer 1

MKAnnotation 要求对象继承自 NSObjectProtocol。为此，您应该让 class 继承自 NSObject。您应该声明您的属性以匹配 MKAnnotation 协议的属性。

示例：

class MapPin : NSObject, MKAnnotation {
    var coordinate: CLLocationCoordinate2D
    var title: String?
    var subtitle: String?

    init(coordinate: CLLocationCoordinate2D, title: String, subtitle: String) {
        self.coordinate = coordinate
        self.title = title
        self.subtitle = subtitle
    }
}

用法：

override func viewDidLoad() {
    super.viewDidLoad()

    // Annotations
    var annotation:MapPin
    annotation.title = "test"         
}