“The greatest masterpiece in literature is only a dictionary out of order.” – Jean Cocteau
- 1 A Quick Guide to the VBA Dictionary
- 2 What is the VBA Dictionary?
- 3 A Dictionary in real world terms
- 4 A Simple Example of using the VBA Dictionary
- 5 Creating a Dictionary
- 6 Adding Items to the Dictionary
- 7 Assigning a Value
- 8 Checking if a Key Exists
- 9 Other useful functions
- 10 The Key and Case Sensitivity
- 11 Reading through the Dictionary
- 12 Troubleshooting the Dictionary
- 13 A Real World Dictionary Example
- 14 When To Use The Dictionary
- 15 What’s Next?
- 16 Get the Free eBook
A Quick Guide to the VBA Dictionary
|Early binding reference||“Microsoft Scripting Runtime”
(Add using Tools->References from the VB menu)
|Declare (early binding)||Dim dict As Scripting.Dictionary|
|Create(early binding)||Set dict = New Scripting.Dictionary|
|Declare (late binding)||Dim dict As Object|
|Create(late binding)||Set dict = CreateObject("Scripting.Dictionary")|
|Add item (key must not already exist)|| dict.Add Key, Value
e.g. dict.Add "Apples", 50
|Change value at key. Automatically adds if the key does not exist.|| dict(Key) = Value
e.g. dict("Oranges") = 60
|Get a value from the dictionary using the key||Value = dict(Key)
e.g. appleCount = dict("Apples")
|Check if key exists||dict.Exists(Key)
e.g. If dict.Exists("Apples") Then
|Remove item||dict.Remove Key
e.g. dict.Remove "Apples"
|Remove all items||dict.RemoveAll|
|Go through all items (for each loop)||Dim key As Variant
For Each key In dict.Keys
Debug.Print key, dict(key)
|Go through all items (for loop - early binding only)||Dim i As Long
For i = 0 To dict.Count - 1
Debug.Print dict.Keys(i), dict.Items(i)
|Get the number of items||dict.Count|
|Make key case sensitive (the dictionary must be empty).||dict.CompareMode = vbBinaryCompare|
|Make key non case sensitive (the dictionary must be empty).||dict.CompareMode = vbTextCompare|
What is the VBA Dictionary?
A Dictionary is similar to a Collection. Using both types, we can name an item when we add it. Imagine we are storing the count of different fruit types.
We could use both a Collection and a Dictionary like this
' Add to Dictionary dict.Add Key:="Apple", Item:=5 ' Add to Collection coll.Add Item:=5, Key:="Apple"
In both cases, we are storing the value 5 and giving it the name “Apple”. We can now get the value of Apple from both types like this
' Get value from Dictionary Total = dict("Apple") ' Get value from Collection Total = coll("Apple")
So far so good. The Collection however, has two major faults
- We cannot check if the key already exists.
- We cannot change the value of an existing item.
The first issue is pretty easy to get around: Check Collection Key exists. The second is more difficult.
The VBA Dictionary does not have these issues. You can check if a Key exists and you can change the Item (Note: you cannot change the Key itself).
For example, we can use the following code to check if we have an item called Apple.
If dict.Exists("Apple") Then dict("Apple") = 78
These may seem very simple differences. However, it means that the Dictionary is very useful for certain tasks. Particularly when we need to retrieve the value of an item.
A Dictionary in real world terms
If you are still not clear about a Dictionary then think of it this way. A real world dictionary has a list of keys and items. The Keys are the words and the Items are the definition.
When you want to find the definition of a word you go straight to that word. You don’t read through every item in the Dictionary.
A second real world example is a phone book(remember those?). The Key in a phone book is the name\address and the Item is the phone number. Again you use the name\address combination to quickly find a phone number.
In Excel the VLookup function works in a similar way to a Dictionary. You look up an item based on a unique value.
A Simple Example of using the VBA Dictionary
The code below give a simple but elegant example of using the Dictionary. It does the following
- Adds three fruit types and a value for each to a Dictionary.
- The user is asked to enter the name of a fruit.
- The code checks if this fruit is in the Dictionary.
- If yes then it displays the fruit name and the value.
- If no then it informs the user the fruit does not exist.
Sub CheckFruit() ' Select Tools->References from the Visual Basic menu. ' Check box beside "Microsoft Scripting Runtime" in the list. Dim dict As New Scripting.Dictionary ' Add to fruit to Dictionary dict.Add key:="Apple", Item:=51 dict.Add key:="Peach", Item:=34 dict.Add key:="Plum,", Item:=43 Dim sFruit As String ' Ask user to enter fruit sFruit = InputBox("Please enter the name of a fruit") If dict.Exists(sFruit) Then MsgBox sFruit & " exists and has value " & dict(sFruit) Else MsgBox sFruit & " does not exist." End If Set dict = Nothing End Sub
This is a simple example but it shows how useful a Dictionary is. We will see a real world example later in the post. Let’s look at the basics of using a Dictionary.
Creating a Dictionary
To use the Dictionary you need to first add the reference.
- Select Tools->References from the Visual Basic menu.
- Find Microsoft Scripting Runtime in the list and place a check in the box beside it.
We declare a dictionary as follows
Dim dict As New Scripting.Dictionary
Dim dict As Scripting.Dictionary Set dict = New Scripting.Dictionary
Creating a Dictionary this way is called “Early Binding”. There is also “Late Binding”. Let’s have a look at what this means.
Early versus Late Binding
To create a Dictionary using Late binding we use the following code. We don’t need to add a reference.
Dim dict As Object Set dict = CreateObject("Scripting.Dictionary")
In technical terms Early binding means we decide exactly what we are using up front. With Late binding this decision is made when the application is running. In simple terms the difference is
- Early binding requires a reference. Late binding doesn’t.
- Early binding allows access to *Intellisense. Late binding doesn’t.
- Early binding may require you to manually add the Reference to the “Microsoft Scripting Runtime” for some users.
(*Intellisense is the feature that shows you the available procedures and properties of an item as you are typing.)
Microsoft recommends that you use early binding in almost all cases.
Adding Items to the Dictionary
|Add||Key, Item||dict.Add "Apples", 50|
We can add items to the dictionary using the Add function. Items can also be added by assigning a value which we will look at in the next section.
Let’s look at the Add function first. The Add function has two parameters: Key and Item. Both must be supplied
dict.Add Key:="Orange", Item:=45 dict.Add "Apple", 66 dict.Add "12/12/2015", "John" dict.Add 1, 45.56
In the first add example above we use the parameter names. You don’t have to do this although it can be helpful when you are starting out.
The Key can be any data type. The Item can be any data type, an object, array, collection or even a dictionary. So you could have a Dictionary of Dictionaries, Array and Collections. But most of the time it will be a value(date, number or text).
If we add a Key that already exists in the Dictionary then we will get the error
The following code will give this error
dict.Add Key:="Orange", Item:=45 ' This line gives an error as key exists already dict.Add Key:="Orange", Item:=75
Assigning a Value
|Assign||Dictionary(Key) = Item||dict("Oranges") = 60|
We can change the value of a key using the following code
dict("Orange") = 75
Assigning a value to Key this way has an extra feature. If the Key does not exist it automatically adds the Key and Item to the dictionary. This would be useful where you had a list of sorted items and only wanted the last entry for each one.
' Adds Orange to the dictionary dict("Orange") = 45 ' Changes the value of Orange to 100 dict("Orange") = 100
Checking if a Key Exists
|Exists||Key||If dict.Exists("Apples") Then|
We can use the Exists function to check if a key exists in the dictionary
' Checks for the key 'Orange' in the dictionary If dict.Exists("Orange") Then MsgBox "The number of oranges is " & dict("Orange") Else MsgBox "There is no entry for Orange in the dictionary." End If
Other useful functions
The three functions in the above table do the following:
- Count – returns the number of items in the Dictionary.
- Remove – removes a given key from the Dictionary.
- RemoveAll – removes all items from the Dictionary
The following sub shows an example of how you would use these functions
Sub AddRemoveCount() Dim dict As New Scripting.Dictionary ' Add some items dict.Add "Orange", 55 dict.Add "Peach", 55 dict.Add "Plum", 55 Debug.Print "The number of items is " & dict.Count ' Remove one item dict.Remove "Orange" Debug.Print "The number of items is " & dict.Count ' Remove all items dict.RemoveAll Debug.Print "The number of items is " & dict.Count End Sub
The Key and Case Sensitivity
Some of the string functions in VBA have a vbCompareMethod. This is used for functions that compare strings. It is used to determine if the case of the letters matter.
The Dictionary uses a similar method. The CompareMode property of the Dictionary is used to determine if the case of the key matters. The settings are
TextCompare: Upper and lower case are considered the same.
BinaryCompare: Upper and lower case are considered different. This is the default.
With the Dictionary we can use these settings to determine if the case of the key matters.
Sub CaseMatters() Dim dict As New Scripting.Dictionary dict.CompareMode = BinaryCompare dict.Add "Orange", 1 ' Prints False because it considers Orange and ORANGE different Debug.Print dict.Exists("ORANGE") Set dict = Nothing End Sub
This time we use TextCompare which means that the case does not matter
Sub CaseMattersNot() Dim dict As New Scripting.Dictionary dict.CompareMode = TextCompare dict.Add "Orange", 1 ' Prints true because it considers Orange and ORANGE the same Debug.Print dict.Exists("ORANGE") Set dict = Nothing End Sub
Note: The Dictionary must be empty when you use the CompareMode property or you will get the error: “Invalid procedure call or argument”.
Things to Watch Out For
BinaryCompare (the case matters) is the default and this can lead to subtle errors. For example, imagine you have the following data in cells A1 to B2.
The following code will create two keys – on for “Orange” and one for “orange”. This is subtle as the only difference is the case of the first letter.
Dim dict As New Scripting.Dictionary dict.add Key:=(Range("A1")), Item:=Range("B1") dict.add Key:=(Range("A2")), Item:=Range("B2")
If you do use TextCompare for the same data you will get an error when you try to add the second key as it considers “Orange” and “orange” the same.
Dim dict As New Scripting.Dictionary dict.CompareMode = TextCompare dict.add Key:=(Range("A1")), Item:=Range("B1") ' This line will give an error as your are trying to add the same key dict.add Key:=(Range("A2")), Item:=Range("B2")
If you use the assign method then it does not take the CompareMode into account. So the following code will still add two keys even though the CompareMode is set to TextCompare.
Sub Assign() Dim dict As New Scripting.Dictionary dict.CompareMode = TextCompare ' Adds two keys dict(Range("A1")) = Range("B1") dict(Range("A2")) = Range("B2") ' Prints 2 Debug.Print dict.Count End Sub
Reading through the Dictionary
We can read through all the items in the Dictionary. We can go through the keys using a For Each loop. We then use the current key to access an item.
Dim k As Variant For Each k In dict.Keys ' Print key and value Debug.Print k, dict(k) Next
We can also loop through the keys although this only works with Early Binding.
Dim i As Long For i = 0 To dict.Count - 1 Debug.Print dict.Keys(i), dict.Items(i) Next i
Troubleshooting the Dictionary
This section covers the common errors you may encounter using the Dictionary.
Issue: You get the error message “User-defined type not defined”
This normally happens when you create the Dictionary but forget to add the reference.
Dim dict As New Scripting.Dictionary
Resolution: Select Tools->Reference from the Visual Basic menu. Place a check in the box beside “Microsoft Scripting Runtime”.
See Section: Creating a Dictionary
Exists is not Working
Issue: You have added a key to the Dictionary but when you use the Exists function it returns false
This is normally an issue with Case Sensitivity(see above).
The following code adds “Apple” as a key. When we check for “apple” it returns false. This is because it takes the case of the letters into account.
dict.Add "Apple", 4 If dict.Exists("apple") Then MsgBox "Exists" Else MsgBox "Does not Exist" End If
You can set the CompareMode property to TextCompare and this will ignore the case.
Dim dict As New Scripting.Dictionary dict.CompareMode = TextCompare
Resolution: Set the CompareMode to TextCompare to ignore case or ensure your data has the correct case.
See Section: The Key and Case Sensitivity
Object Variable Error
Issue: You get the error message “Object variable or With block variable not set” when you try to use the Dictionary.
The normally happens when you forget to use New before you use the Dictionary. For example, the following code will cause this error
Dim dict As Scripting.Dictionary ' This line will give "Object variable..." error dict.Add "Apple", 4
Resolution: Use the New keyword when creating the Dictionary
Dim dict As New Scripting.Dictionary
Dim dict As Scripting.Dictionary Set dict = New Scripting.Dictionary
See Section: Creating a Dictionary
Useful Tips for Troubleshooting the Dictionary
If you are investigating an issue with the Dictionary it can be useful to see the contents.
Use the following sub to Print each Key and Item to the Immediate Window(Ctrl + G).
Sub PrintContents(dict As Scripting.Dictionary) Dim k As Variant For Each k In dict.Keys ' Print key and value Debug.Print k, dict(k) Next End Sub
You can use it like this
Dim dict As Scripting.Dictionary Set dict = New Scripting.Dictionary ' Add items to Dictionary here ' Print the contents of the Dictionary to the Immediate Window PrintContents dict
If you are stepping through the code you can also add dict.Count to the Watch Window to see how many items are currently in the Dictionary. Right-click anywhere in the code window and select Add Watch. Type dict.Count into the text box and click Ok.
You can also use the Dictionary itself as a Watch. Add Dict to the Watch window. If you click on the plus sign you will see the contents of the Dictionary. This can be useful but it only shows the key and not the item.
Note: You can only view Watches when the code is running.
A Real World Dictionary Example
Let’s have a look at a real world example of using a dictionary. Our data for this example is the World Cup Final matches from 2014.
Our task here is to get the number of goals scored by each team.
The first thing we need to do is to read all the data. The following code reads through all the matches and prints the names of the two teams involved.
Sub GetTotals() ' Get worksheet Dim wk As Worksheet Set wk = ThisWorkbook.Worksheets("2014") ' Get range for all the matches Dim rgMatches As Range Set rgMatches = wk.Range("A1").CurrentRegion Dim sTeam1 As String, sTeam2 As String Dim lGoals1 As Long, lGoals2 As Long Dim row As Range For Each row In rgMatches.Rows ' read the data from each match sTeam1 = row.Cells(1, 5) sTeam2 = row.Cells(1, 9) lGoals1 = row.Cells(1, 6) lGoals2 = row.Cells(1, 7) ' Print each teams/goals to Immediate Window(Ctrl + G) Debug.Print sTeam1, sTeam2, lGoals1, lGoals2 Next row End Sub
What we want to do now is to store each team and the goals they scored. When we meet a team for the first time we add the name as a Key and the number of goals as the Item.
If the team has already been added then we add the goals they scored in the current match to their total.
Using a Dictionary, we can easily check if the team already exists. We can also update the value for this team.
If dict.Exists(sTeam1) Then ' If exists add to total dict(sTeam1) = dict(sTeam1) + lGoals1 Else ' if doesn't exist then add dict(sTeam1) = lGoals1 End If
We write out the values from the Dictionary to the worksheet as follows
Public Sub WriteDictionary(dict As Scripting.Dictionary _ , shReport As Worksheet) shReport.Cells.Clear Dim k As Variant, lRow As Long lRow = 1 For Each k In dict.Keys shReport.Cells(lRow, 1) = k shReport.Cells(lRow, 2) = dict(k) lRow = lRow + 1 Next End Sub
We obviously want the scores to be sorted. It is much easier to read this way. There is no easy way to sort a Dictionary. The way to do it is to copy all the items to an array. Sort the array and copy the items back to a Dictionary.
What we can do is sort the data once it has been written to the worksheet. We can use the following code to do this
Public Sub SortByScore(shReport As Worksheet) Dim rg As Range Set rg = shReport.Range("A1").CurrentRegion rg.sort rg.Columns("B"), xlDescending End Sub
Our final GetTotals Sub looks like this
Sub GetTotals() ' Create dictionary Dim dict As New Scripting.Dictionary ' Get worksheet Dim sh As Worksheet Set sh = ThisWorkbook.Worksheets("2014") ' Get range Dim rgMatches As Range Set rgMatches = sh.Range("A1").CurrentRegion Dim sTeam1 As String, sTeam2 As String Dim lGoals1 As Long, lGoals2 As Long Dim i As Long For i = 2 To rgMatches.Rows.Count sTeam1 = rgMatches.Cells(i, 5) sTeam2 = rgMatches.Cells(i, 9) lGoals1 = rgMatches.Cells(i, 6) lGoals2 = rgMatches.Cells(i, 7) If dict.Exists(sTeam1) Then ' If exists add to total dict(sTeam1) = dict(sTeam1) + lGoals1 Else ' if doesn't exist then add dict(sTeam1) = lGoals1 End If If dict.Exists(sTeam2) Then ' If exists add to total dict(sTeam2) = dict(sTeam2) + lGoals2 Else ' if doesn't exist then add dict(sTeam2) = lGoals2 End If Next i ' Get the report worksheet Dim shReport As Worksheet Set shReport = ThisWorkbook.Worksheets("Report") ' Write the teams and scores to the worksheet WriteDictionary dict, shReport ' Sort the range SortByScore shReport ' Clean up Set dict = Nothing End Sub
When you run this code you will get the following results
When To Use The Dictionary
So when should you use the VBA Dictionary? When you have a task where
- You have a list of unique items e.g. countries, invoice numbers, customer name and addresses, project ids, product names etc.
- You need to retrieve the value of a unique item.
If you want to read about more VBA topics you can view a complete list of my posts here. I also have a free eBook(see below) which you will find useful if you are new to VBA.
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