Does VBA have Dictionary Structure

Question

Does VBA have dictionary structure  Like key lt  value array

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VBA has the collection object       Dim c As Collection     Set c   New Collection     c Add  Data1    Key1      c Add  Data2    Key2      c Add  Data3    Key3       Insert data via key into cell A1     Range  A1   Value   c Item  Key2     The Collection object performs key-based lookups using a hash so it s quick     You can use a Contains   function to check whether a particular collection contains a key   Public Function Contains col As Collection  key As Variant  As Boolean     On Error Resume Next     col key    Just try it  If it fails  Err Number will be nonzero      Contains    Err Number   0      Err Clear End Function   Edit 24 June 2015  Shorter Contains   thanks to  TWiStErRob   Edit 25 September 2015  Added Err Clear   thanks to  scipilot

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If by any reason  you can t install additional features to your Excel or don t want to  you can use arrays as well  at least for simple problems  As WhatIsCapital you put name of the country and the function returns you its capital   Sub arrays   Dim WhatIsCapital As String  Country As Array  Capital As Array  Answer As String  WhatIsCapital    Sweden   Country   Array  UK    Sweden    Germany    France   Capital   Array  London    Stockholm    Berlin    Paris    For i   0 To 10     If WhatIsCapital   Country i  Then Answer   Capital i  Next i  Debug Print Answer  End Sub

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An additional dictionary example that is useful for containing frequency of occurence   Outside of loop   Dim dict As New Scripting dictionary Dim MyVar as String   Within a loop    dictionary If dict Exists MyVar  Then     dict Item MyVar    dict Item MyVar    1  increment Else     dict Item MyVar    1  set as 1st occurence End If   To check on frequency   Dim i As Integer For i   0 To dict Count - 1   lower index 0  instead of 1      Debug Print dict Items i   amp       amp  dict Keys i  Next i

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Yes   Set a reference to MS Scripting runtime   Microsoft Scripting Runtime    As per  regjo s comment  go to Tools- References and tick the box for  Microsoft Scripting Runtime      Create a dictionary instance using the code below   Set dict   CreateObject  Scripting Dictionary     or  Dim dict As New Scripting Dictionary    Example of use   If Not dict Exists key  Then      dict Add key  value End If    Don t forget to set the dictionary to Nothing when you have finished using it   Set dict   Nothing

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Yes   For VB6  VBA  Excel   and VB NET

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Building off cjrh s answer  we can build a Contains function requiring no labels  I don t like using labels    Public Function Contains Col As Collection  Key As String  As Boolean     Contains   True     On Error Resume Next         err Clear         Col  Key          If err Number  lt  gt  0 Then             Contains   False             err Clear         End If     On Error GoTo 0 End Function     For a project of mine  I wrote a set of helper functions to make a Collection behave more like a Dictionary  It still allows recursive collections  You ll notice Key always comes first because it was mandatory and made more sense in my implementation  I also used only String keys  You can change it back if you like   Set  I renamed this to set because it will overwrite old values   Private Sub cSet ByRef Col As Collection  Key As String  Item As Variant      If  cHas Col  Key   Then Col Remove Key     Col Add Array Key  Item   Key End Sub   Get  The err stuff is for objects since you would pass objects using set and variables without  I think you can just check if it s an object  but I was pressed for time   Private Function cGet ByRef Col As Collection  Key As String  As Variant     If Not cHas Col  Key  Then Exit Function     On Error Resume Next         err Clear         Set cGet   Col Key  1          If err Number   13 Then             err Clear             cGet   Col Key  1          End If     On Error GoTo 0     If err Number  lt  gt  0 Then Call err raise err Number  err Source  err Description  err HelpFile  err HelpContext  End Function   Has  The reason for this post     Public Function cHas Col As Collection  Key As String  As Boolean     cHas   True     On Error Resume Next         err Clear         Col  Key          If err Number  lt  gt  0 Then             cHas   False             err Clear         End If     On Error GoTo 0 End Function   Remove  Doesn t throw if it doesn t exist  Just makes sure it s removed   Private Sub cRemove ByRef Col As Collection  Key As String      If cHas Col  Key  Then Col Remove Key End Sub   Keys  Get an array of keys   Private Function cKeys ByRef Col As Collection  As String       Dim Initialized As Boolean     Dim Keys   As String      For Each Item In Col         If Not Initialized Then             ReDim Preserve Keys 0              Keys UBound Keys     Item 0              Initialized   True         Else             ReDim Preserve Keys UBound Keys    1              Keys UBound Keys     Item 0          End If     Next Item      cKeys   Keys End Function

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VBA can use the dictionary structure of Scripting Runtime  And its implementation is actually a fancy one - just by doing myDict x    y  it checks whether there is a key x in the dictionary and if there is not such  it even creates it  If it is there  it uses it  And it does not  quot yell quot  or  quot complain quot  about this extra step  performed  quot under the hood quot   Of course  you may check explicitly  whether a key exists with Dictionary Exists key   Thus  these 5 lines  If myDict exists  quot B quot   Then     myDict  quot B quot     myDict  quot B quot     i   3 Else     myDict Add  quot B quot   i   3 End If  are the same as this 1 liner - myDict  quot B quot     myDict  quot B quot     i   3  Check it out  Sub TestMe        Dim myDict As Object  i As Long  myKey As Variant     Set myDict   CreateObject  quot Scripting Dictionary quot            For i   1 To 3         Debug Print myDict Exists  quot A quot           myDict  quot A quot     myDict  quot A quot     i         myDict  quot B quot     myDict  quot B quot     5     Next i          For Each myKey In myDict keys         Debug Print myKey  myDict myKey      Next myKey  End Sub

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All the others have already mentioned the use of the scripting runtime version of the Dictionary class  If you are unable to use this DLL you can also use this version  simply add it to your code   https   github com VBA-tools VBA-Dictionary blob master Dictionary cls  It is identical to Microsoft s version

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VBA does not have an internal implementation of a dictionary  but from VBA you can still use the dictionary object from MS Scripting Runtime Library   Dim d Set d   CreateObject  Scripting Dictionary   d Add  a    aaa  d Add  b    bbb  d Add  c    ccc   If d Exists  c   Then     MsgBox d  c   End If

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The scripting runtime dictionary seems to have a bug that can ruin your design at advanced stages      If the dictionary value is an array  you cannot update values of elements contained in the array through a reference to the dictionary

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You can access a non-Native HashTable through System Collections HashTable  HashTable  Represents a collection of key value pairs that are organized based on the hash code of the key   Not sure you would ever want to use this over Scripting Dictionary but adding here for the sake of completeness  You can review the methods in case there are some of interest e g  Clone  CopyTo Example  Option Explicit  Public Sub UsingHashTable        Dim h As Object     Set h   CreateObject  quot System Collections HashTable quot           h Add  quot A quot   1       h Add  quot A quot   1     lt  lt  Will throw duplicate key error     h Add  quot B quot   2     h  quot B quot     2            Dim keys As mscorlib IEnumerable  Need to cast in order to enumerate   https   stackoverflow com a 56705428 6241235          Set keys   h keys          Dim k As Variant          For Each k In keys         Debug Print k  h k                        outputs the key and its associated value     Next      End Sub   This answer by  MathieuGuindon gives plenty of detail about HashTable and also why it is necessary to use mscorlib IEnumerable  early bound reference to mscorlib  in order to enumerate the key value pairs

[vba] Does VBA have Dictionary Structure?

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