尝试用swift字典中的键字符串填充数组。
var componentArray: [String]
let dict = NSDictionary(contentsOfFile: NSBundle.mainBundle().pathForResource("Components", ofType: "plist")!)
componentArray = dict.allKeys
这将返回一个错误:'AnyObject'与string不相同
也试过
componentArray = dict.allKeys as String
but get: 'String'不能转换为[String]
当前回答
extension Array {
public func toDictionary<Key: Hashable>(with selectKey: (Element) -> Key) -> [Key:Element] {
var dict = [Key:Element]()
for element in self {
dict[selectKey(element)] = element
}
return dict
}
}
其他回答
数组从字典键在Swift
componentArray = [String] (dict.keys)
// Old version (for history)
let keys = dictionary.keys.map { $0 }
let keys = dictionary?.keys.map { $0 } ?? [T]()
// New more explained version for our ducks
extension Dictionary {
var allKeys: [Dictionary.Key] {
return self.keys.map { $0 }
}
}
在Swift 3中，Dictionary有一个keys属性。Keys有以下声明:
var keys: LazyMapCollection<Dictionary<Key, Value>, Key> { get }
仅包含字典键的集合。
注意，LazyMapCollection可以很容易地用Array的init(_:)初始化器映射到Array。
从NSDictionary到[String]
下面的iOS AppDelegate类片段展示了如何从NSDictionary中使用keys属性获得一个字符串数组([String]):
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
let string = Bundle.main.path(forResource: "Components", ofType: "plist")!
if let dict = NSDictionary(contentsOfFile: string) as? [String : Int] {
let lazyMapCollection = dict.keys
let componentArray = Array(lazyMapCollection)
print(componentArray)
// prints: ["Car", "Boat"]
}
return true
}
从[String: Int]到[String]
下面的Playground代码以更通用的方式展示了如何使用keys属性从具有字符串键和整型值([String: Int])的字典中获得一个字符串数组([String]):
let dictionary = ["Gabrielle": 49, "Bree": 32, "Susan": 12, "Lynette": 7]
let lazyMapCollection = dictionary.keys
let stringArray = Array(lazyMapCollection)
print(stringArray)
// prints: ["Bree", "Susan", "Lynette", "Gabrielle"]
从[Int: String]到[String]
下面的Playground代码展示了如何从具有整型键和字符串值([Int: String])的字典中使用keys属性获得一个字符串数组([String]):
let dictionary = [49: "Gabrielle", 32: "Bree", 12: "Susan", 7: "Lynette"]
let lazyMapCollection = dictionary.keys
let stringArray = Array(lazyMapCollection.map { String($0) })
// let stringArray = Array(lazyMapCollection).map { String($0) } // also works
print(stringArray)
// prints: ["32", "12", "7", "49"]
字典allKeys不是一个字符串。它是一个[String]，就像错误消息告诉你的那样(当然，假设键都是字符串;这正是你所说的)。
所以，要么首先将componentArray键入为[AnyObject]，因为这是它在Cocoa API中键入的方式，要么，如果你强制转换dict。allKeys，将它转换为[String]，因为这是你键入componentArray的方式。
dict.keys.sorted()
给出[String] https://developer.apple.com/documentation/swift/array/2945003-sorted
