swift中字典键的数组

8 回答

• 2

  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
      }
  }
  

  回复于 2024-04-27T18:49:26+08:00
• 0

  dict.allKeys 不是字符串 . 它是一个 [String] ，正如错误消息告诉你的那样（当然，假设键都是字符串;这正是你在说的时断言） .

  所以，要么首先输入 componentArray 作为 [AnyObject] ，因为这是在Cocoa API中输入的方式，否则，如果你强制转换 dict.allKeys ，则将其强制转换为 [String] ，因为这就是你输入 componentArray 的方式 .

  回复于 2024-04-27T18:49:26+08:00
• 436

  Swift 3和Swift 4

  componentArray = Array(dict.keys) // for Dictionary
  
  componentArray = dict.allKeys // for NSDictionary
  

  回复于 2024-04-27T18:49:26+08:00
• 36

  使用Swift 3， Dictionary 具有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可以很容易地映射到带有 Array 的init(_:)初始化程序的 Array .

  ---

  从NSDictionary到[String]

  以下iOS AppDelegate 类代码段显示如何使用 NSDictionary 中的 keys 属性获取字符串数组（ [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]

  以更一般的方式，以下Playground代码显示如何使用字符串键和整数值（ [String: Int] ）的字典中的 keys 属性获取字符串数组（ [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]

  以下Playground代码显示如何使用带有整数键和字符串值（ [Int: String] ）的字典中的 keys 属性获取字符串数组（ [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"]
  

  回复于 2024-04-27T18:49:26+08:00
• 47

  Swift中字典键中的数组

  componentArray = [String] (dict.keys)
  

  回复于 2024-04-27T18:49:26+08:00
• 8

  NSDictionary 是 Class(pass by reference)
  
  Dictionary 是 Structure(pass by value ）
  
  ======来自NSDictionary的数组======

  NSDictionary的 allKeys 和 allValues 获取类型为 [Any] 的属性 .
  

  let objesctNSDictionary = 
      NSDictionary.init(dictionary: ["BR": "Brazil", "GH": "Ghana", "JP": "Japan"])
              let objectArrayOfAllKeys:Array = objesctNSDictionary.allKeys
              let objectArrayOfAllValues:Array = objesctNSDictionary.allValues
              print(objectArrayOfAllKeys)
              print(objectArrayOfAllValues)
  

  ======数组来自词典======

  Apple参考 Dictionary's keys 和 values 属性 .
  

  

  let objectDictionary:Dictionary = 
              ["BR": "Brazil", "GH": "Ghana", "JP": "Japan"]
      let objectArrayOfAllKeys:Array = Array(objectDictionary.keys)          
      let objectArrayOfAllValues:Array = Array(objectDictionary.values)
      print(objectArrayOfAllKeys)
      print(objectArrayOfAllValues)
  

  回复于 2024-04-27T18:49:26+08:00
• 0

  这个答案将用于swift字典w / String键 . Like this one below .

  let dict: [String: Int] = ["hey": 1, "yo": 2, "sup": 3, "hello": 4, "whassup": 5]
  

  这是我将使用的扩展 .

  extension Dictionary {
    func allKeys() -> [String] {
      guard self.keys.first is String else {
        debugPrint("This function will not return other hashable types. (Only strings)")
        return []
      }
      return self.flatMap { (anEntry) -> String? in
                            guard let temp = anEntry.key as? String else { return nil }
                            return temp }
    }
  }
  

  我稍后会使用这个来获取所有密钥 .

  let componentsArray = dict.allKeys()
  

  回复于 2024-04-27T18:49:26+08:00
• 2

  dict.keys.sorted()
  

  给[String] https://developer.apple.com/documentation/swift/array/2945003-sorted

  回复于 2024-04-27T18:49:26+08:00