Determining if Swift dictionary contains key and obtaining any of its values

Question

I am currently using the following  clumsy  pieces of code for determining if a  non-empty  Swift dictionary contains a given key and for obtaining one  any  value from the same dictionary   How can one put this more elegantly in Swift      excerpt from method that determines if dict contains key if let     dict key        return true   else       return false       excerpt from method that obtains first value from dict for     value  in dict       return value

User · Answer

if dictionayTemp  quantity      nil            write your code

User · Answer

You don t need any special code to do this  because it is what a dictionary already does  When you fetch dict key  you know whether the dictionary contains the key  because the Optional that you get back is not nil  and it contains the value    So  if you just want to answer the question whether the dictionary contains the key  ask   let keyExists   dict key     nil   If you want the value and you know the dictionary contains the key  say   let val   dict key     But if  as usually happens  you don t know it contains the key - you want to fetch it and use it  but only if it exists - then use something like if let   if let val   dict key           now val is not nil and the Optional has been unwrapped  so use it

User · Answer

The accepted answer let keyExists   dict key     nil will not work if the Dictionary contains the key but has a value of nil     If you want to be sure the Dictionary does not contain the key at all use this  tested in Swift 4    if dict keys contains key         contains key   else         does not contain key

User · Answer

Looks like you got what you need from  matt  but if you want a quick way to get a value for a key  or just the first value if that key doesn   t exist   extension Dictionary       func keyedOrFirstValue key  Key  - gt  Value               if key not found  replace the nil with             the first element of the values collection         return self key     first self values             note  this is still an optional  because the            dictionary could be empty           let d     one   red    two   blue    d keyedOrFirstValue  one        Some  red   d keyedOrFirstValue  two        Some  blue   d keyedOrFirstValue  three        Some  red       Note  no guarantees what you ll actually get as the first value  it just happens in this case to return    red

User · Answer

My solution for a cache implementation that stores optional NSAttributedString   public static var attributedMessageTextCache       String  NSAttributedString          if attributedMessageTextCache index forKey   key      nil               if let attributedMessageText   TextChatCache attributedMessageTextCache  key                         return attributedMessageText                   return nil            TextChatCache attributedMessageTextCache  key      some  none      return nil

User · Answer

Here is what works for me on Swift 3  let      dict key  map    0 as  String

User · Answer

Why not simply check for dict keys contains key   Checking for dict key     nil will not work in cases where the value is nil  As with a dictionary  String  String   for example

[swift] Determining if Swift dictionary contains key and obtaining any of its values

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