ios swift中字典键的数组

Array from dictionary keys in swift

提问by Kyle Goslan

Trying to fill an array with strings from the keys in a dictionary in swift.

试图用 swift 字典中键的字符串填充数组。

var componentArray: [String]

let dict = NSDictionary(contentsOfFile: NSBundle.mainBundle().pathForResource("Components", ofType: "plist")!)
componentArray = dict.allKeys

This returns an error of: 'AnyObject' not identical to string

这将返回错误：“AnyObject”与字符串不同

Also tried

也试过

componentArray = dict.allKeys as String 

but get: 'String' is not convertible to [String]

但得到：'String' 不能转换为 [String]

回答by Andrius Steponavi?ius

Swift 3 & Swift 4

斯威夫特 3 和斯威夫特 4

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

componentArray = dict.allKeys // for NSDictionary

回答by Imanou Petit

With Swift 3, Dictionaryhas a keysproperty. keyshas the following declaration:

有了Swift 3，Dictionary就有了keys属性。keys有以下声明：

var keys: LazyMapCollection<Dictionary<Key, Value>, Key> { get }

A collection containing just the keys of the dictionary.

仅包含字典键的集合。

Note that LazyMapCollectionthat can easily be mapped to an Arraywith Array's init(_:)initializer.

请注意，LazyMapCollection这可以很容易地映射到ArraywithArray的init(_:)初始化程序。

---

---

From NSDictionaryto [String]

从NSDictionary到[String]

The following iOS AppDelegateclass snippet shows how to get an array of strings ([String]) using keysproperty from a NSDictionary:

以下 iOSAppDelegate类片段展示了如何[String]使用keysa 中的属性获取字符串数组 ( ) NSDictionary：

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
}

---

---

From [String: Int]to [String]

从[String: Int]到[String]

In a more general way, the following Playground code shows how to get an array of strings ([String]) using keysproperty from a dictionary with string keys and integer values ([String: Int]):

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

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"]

---

---

From [Int: String]to [String]

从[Int: String]到[String]

The following Playground code shows how to get an array of strings ([String]) using keysproperty from a dictionary with integer keys and string values ([Int: String]):

以下 Playground 代码显示了如何[String]使用keys具有整数键和字符串值 ( [Int: String])的字典中的属性获取字符串数组( )：

let dictionary = [49: "Gabrielle", 32: "Bree", 12: "Susan", 7: "Lynette"]
let lazyMapCollection = dictionary.keys

let stringArray = Array(lazyMapCollection.map { String(
componentArray = [String] (dict.keys)
) })
// let stringArray = Array(lazyMapCollection).map { String(
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
    }
}
) } // also works
print(stringArray)
// prints: ["32", "12", "7", "49"]

回答by Santo

Array from dictionary keys in Swift

Swift 中字典键的数组

  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)

回答by matt

dict.allKeysis not a String. It is a [String], exactly as the error message tells you (assuming, of course, that the keys areall strings; this is exactly what you are asserting when you say that).

dict.allKeys不是字符串。它是一个[String]，正如错误消息告诉您的那样（当然，假设所有键都是字符串；这正是您所说的断言）。

So, either start by typing componentArrayas [AnyObject], because that is how it is typed in the Cocoa API, or else, if you cast dict.allKeys, cast it to [String], because that is how you have typed componentArray.

因此，要么从输入componentArrayas开始[AnyObject]，因为这是在 Cocoa API 中输入的方式，或者，如果您强制转换dict.allKeys，则将其强制转换为[String]，因为这就是您输入的方式componentArray。

回答by Jitesh Desai

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)

回答by Darshan Panchal

NSDictionaryis Class(pass by reference)Dictionaryis Structure(pass by value) ====== Array from NSDictionary ======

NSDictionary是类（按引用传递）字典是结构（按值传递） ====== NSDictionary 中的数组 ======

NSDictionary has allKeysand allValuesget properties with type [Any].

NSDictionary 具有allKeys和allValues获取类型为[Any] 的属性。

dict.keys.sorted() 

====== Array From Dictionary ======

====== 字典中的数组 ======

Apple reference for Dictionary'skeysand valuesproperties.

字典的键和值属性的Apple 参考。

Array.init<S>(_ s: S) where Element == S.Element, S : Sequence

回答by Jlam

func cacheImagesWithNames(names: [String]) {
    // custom image loading and caching
 }

let namedHues: [String: Int] = ["Vermillion": 18, "Magenta": 302,
        "Gold": 50, "Cerise": 320]
let colorNames = Array(namedHues.keys)
cacheImagesWithNames(colorNames)

print(colorNames)
// Prints "["Gold", "Cerise", "Magenta", "Vermillion"]"

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

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

回答by Chris Graf

From the official Array Apple documentation:

来自官方Array Apple 文档：

init(_:)- Creates an array containing the elements of a sequence.

init(_:)- 创建一个包含序列元素的数组。

Declaration

宣言

var dict = ["key1":"Value1", "key2":"Value2"]

let k = dict.keys

var a: [String]()
a.append(contentsOf: k)

Parameters

参数

s- The sequence of elements to turn into an array.

s- 要变成数组的元素序列。

Discussion

讨论

You can use this initializer to create an array from any other type that conforms to the Sequence protocol...You can also use this initializer to convert a complex sequence or collection type back to an array.For example, the keys property of a dictionary isn't an array with its own storage, it's a collection that maps its elements from the dictionary only when they're accessed, saving the time and space needed to allocate an array. If you need to pass those keys to a method that takes an array, however, use this initializer to convert that list from its type of LazyMapCollection<Dictionary<String, Int>, Int> to a simple [String].

您可以使用此初始化程序从符合 Sequence 协议的任何其他类型创建数组……您还可以使用此初始化程序将复杂序列或集合类型转换回数组。例如，字典的 keys 属性不是一个拥有自己存储空间的数组，它是一个仅在访问时才从字典中映射元素的集合，从而节省了分配数组所需的时间和空间。但是，如果您需要将这些键传递给采用数组的方法，请使用此初始化程序将该列表从其类型转换为LazyMapCollection<Dictionary<String, Int>, Int> to a simple [String].

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

回答by Siddharth Kavthekar

Swift 5

斯威夫特 5

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 }
  }
}

This works for me.

这对我有用。

回答by jnblanchard

This answer will be for swift dictionary w/ String keys. Like this one below.

此答案适用于带有字符串键的 swift 字典。像下面这个。

let componentsArray = dict.allKeys()

Here's the extension I'll use.

这是我将使用的扩展名。

##代码##

And I'll get all the keys later using this.

稍后我将使用它获取所有密钥。

##代码##