Array from dictionary keys in swift

Question

Trying to fill an array with strings from the keys in a dictionary in swift   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  Also tried  componentArray   dict allKeys as String    but get   String  is not convertible to  String

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Swift 3  amp  Swift 4  componentArray   Array dict keys     for Dictionary  componentArray   dict allKeys    for NSDictionary

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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

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This answer will be for swift dictionary w  String keys  Like this one below   let dict   String  Int      hey   1   yo   2   sup   3   hello   4   whassup   5    Here s the extension I ll use   extension Dictionary     func allKeys   - gt   String        guard self keys first is String else         debugPrint  This function will not return other hashable types   Only strings          return              return self flatMap    anEntry  - gt  String  in                           guard let temp   anEntry key as  String else   return nil                             return temp           And I ll get all the keys later using this   let componentsArray   dict allKeys

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You can use dictionary map like this    let myKeys   String    myDictionary map String  0 key      The explanation   Map iterates through the myDictionary and accepts each key and value pair as  0  From here you can get  0 key or  0 value  Inside the trailing closure     you can transform each element and return that element  Since you want  0 and you want it as a string then you convert using String  0 key   You collect the transformed elements to an array of strings

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dict allKeys is not a String  It is a  String   exactly as the error message tells you  assuming  of course  that the keys are all strings  this is exactly what you are asserting when you say that    So  either start by typing componentArray as  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

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Array from dictionary keys in Swift  componentArray    String   dict keys

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Swift 5  var dict     key1   Value1    key2   Value2    let k   dict keys  var a   String    a append contentsOf  k    This works for me

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With Swift 3  Dictionary has a keys property  keys has the following declaration  var keys  LazyMapCollection lt Dictionary lt Key  Value gt   Key gt    get     A collection containing just the keys of the dictionary   Note that LazyMapCollection that can easily be mapped to an Array with Array s init     initializer   From NSDictionary to  String  The following iOS AppDelegate class snippet shows how to get an array of strings   String   using keys property from a NSDictionary   func application   application  UIApplication  didFinishLaunchingWithOptions launchOptions   UIApplicationLaunchOptionsKey  Any    - gt  Bool       let string   Bundle main path forResource   quot Components quot   ofType   quot plist quot        if let dict   NSDictionary contentsOfFile  string  as   String   Int            let lazyMapCollection   dict keys                  let componentArray   Array lazyMapCollection          print componentArray             prints    quot Car quot    quot Boat quot                  return true     From  String  Int  to  String  In a more general way  the following Playground code shows how to get an array of strings   String   using keys property from a dictionary with string keys and integer values   String  Int    let dictionary     quot Gabrielle quot   49   quot Bree quot   32   quot Susan quot   12   quot Lynette quot   7  let lazyMapCollection   dictionary keys  let stringArray   Array lazyMapCollection  print stringArray     prints    quot Bree quot    quot Susan quot    quot Lynette quot    quot Gabrielle quot     From  Int  String  to  String  The following Playground code shows how to get an array of strings   String   using keys property from a dictionary with integer keys and string values   Int  String    let dictionary    49   quot Gabrielle quot   32   quot Bree quot   12   quot Susan quot   7   quot Lynette quot   let lazyMapCollection   dictionary keys      let stringArray   Array lazyMapCollection map   String  0        let stringArray   Array lazyMapCollection  map   String  0       also works print stringArray     prints    quot 32 quot    quot 12 quot    quot 7 quot    quot 49 quot

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From the official Array Apple documentation   init     - Creates an array containing the elements of a sequence   Declaration  Array init lt S gt    s  S  where Element    S Element  S   Sequence   Parameters  s - The sequence of elements to turn into an array   Discussion     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 lt Dictionary lt String  Int gt   Int gt  to a simple  String     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

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extension Array       public func toDictionary lt Key  Hashable gt  with selectKey   Element  - gt  Key  - gt   Key Element            var dict    Key Element            for element in self               dict selectKey element     element                   return dict

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dict keys sorted      that gives  String  https   developer apple com documentation swift array 2945003-sorted

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NSDictionary is Class pass by reference    Dictionary is Structure pass by value           Array from NSDictionary         NSDictionary has allKeys and allValues get properties with  type  Any      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           Array From Dictionary          Apple reference for Dictionary s keys and values properties      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

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