无法用索引类型“字符串"下标"[NSObject:AnyObject]"类型的值 [英] Cannot subscript a value of type '[NSObject : AnyObject]' with an index of type 'String'

问题描述

我在下面的代码片段中遇到错误.每当我尝试构建它时，编译器都会抱怨:

I been getting errors on the snippet of code below. Every time I try to build it, the compiler complains:

不能用索引类型为"String"的下标"[NSObject:AnyObject]"的值

Cannot subscript a value of type '[NSObject : AnyObject]' with an index of type 'String'

这是所有荣耀的代码:

import Foundation
import MapKit

enum LocationKey: String {
    case Latitude = "lat"
    case Longitude = "long"
    case Title = "title"
}

extension MKPointAnnotation {
    var propertyState: [NSObject: AnyObject] {
        get {
            return [ LocationKey.Longitude.rawValue as NSObject: NSNumber(value: coordinate.latitude),
                     LocationKey.Longitude.rawValue as NSObject: NSNumber(value: coordinate.longitude),
                     LocationKey.Title.rawValue as NSObject: title as AnyObject]
        }
        set {
            let lat = (newValue[LocationKey.Latitude.rawValue] as NSNumber).doubleValue
            let long = (newValue[LocationKey.Longitude.rawValue] as NSNumber).doubleValue
            coordinate = CLLocationCoordinate2D(latitude: lat, longitude: long)
            title = newValue[LocationKey.Title.rawValue] as NSString
        }
    }
}

我真正遇到麻烦的代码行是:

The lines of code that I really have trouble with are:

let lat = (newValue[LocationKey.Latitude.rawValue] as NSNumber).doubleValue
let long = (newValue[LocationKey.Longitude.rawValue] as NSNumber).doubleValue
title = newValue[LocationKey.Title.rawValue] as NSString

感谢一堆！

推荐答案

您的代码太复杂了.所有值都是值类型，因此将字典声明为[String:Any] –可以解决该错误–并消除对NSNumber和AnyObject的所有丑陋类型强制转换.

Your code is too complicated. All values are value type so declare the dictionary as [String:Any] – which solves the error by the way – and get rid of all ugly type casts to NSNumber and AnyObject.

import Foundation
import MapKit

enum LocationKey: String {
    case latitude = "lat"
    case longitude = "long"
    case title = "title"
}


extension MKPointAnnotation {
    var propertyState: [String: Any] {
        get {
            return [ LocationKey.latitude.rawValue: coordinate.latitude,
                     LocationKey.longitude.rawValue: coordinate.longitude,
                     LocationKey.title.rawValue: title ?? ""]
        }
        set {
            guard let lat = newValue[LocationKey.latitude.rawValue] as? CLLocationDegrees,
            let long = newValue[LocationKey.longitude.rawValue] as? CLLocationDegrees else { return }
            coordinate = CLLocationCoordinate2D(latitude: lat, longitude: long)
            title = newValue[LocationKey.title.rawValue] as? String
        }
    }
}

您甚至可以将枚举用作键

You can even use the enum as key

extension MKPointAnnotation {
    var propertyState: [LocationKey: Any] {
        get {
            return [ .latitude: coordinate.latitude,
                     .longitude: coordinate.longitude,
                     .title: title ?? ""]
        }
        set {
            guard let lat = newValue[.latitude] as? CLLocationDegrees,
            let long = newValue[.longitude] as? CLLocationDegrees else { return }
            coordinate = CLLocationCoordinate2D(latitude: lat, longitude: long)
            title = newValue[.title] as? String
        }
    }
}

注意:您的吸气剂使用LocationKey.Longitude两次，这将导致编译器错误.

Note: Your getter uses LocationKey.Longitude twice which will cause a compiler error.

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