VBA string interpolation syntax - vba

Question

What is the VBA string interpolation syntax? Does it exist?
I would to to use Excel VBA to format a string.
I have a variable foo that I want to put in a string for a range.
Dim row as Long
row = 1
myString = "$row:$row"
I would like the $row in the string to be interpolated as "1"

Answer 1

You could also build a custom Format function.
Public Function Format(ParamArray arr() As Variant) As String
Dim i As Long
Dim temp As String
temp = CStr(arr(0))
For i = 1 To UBound(arr)
temp = Replace(temp, "{" & i - 1 & "}", CStr(arr(i)))
Next
Format = temp
End Function
The usage is similar to C# except that you can't directly reference variables in the string. E.g. Format("This will {not} work") but Format("This {0} work", "will").
Public Sub Test()
Dim s As String
s = "Hello"
Debug.Print Format("{0}, {1}!", s, "World")
End Sub
Prints out Hello, World! to the Immediate Window.

Answer 2

This works well enough, I believe.
Dim row as Long
Dim s as String
row = 1
s = "$" & row & ":$" & row
Unless you want something similar to Python's or C#'s {} notation, this is the standard way of doing it.

Answer 3

Using Key\Value Pairs
Another alternative to mimic String interpolation is to pass in key\value pairs as a ParamArray and replace the keys accordingly.
One note is that an error should be raised if there are not an even number of elements.
' Returns a string that replaced special keys with its associated pair value.
Public Function Inject(ByVal source As String, ParamArray keyValuePairs() As Variant) As String
If (UBound(keyValuePairs) - LBound(keyValuePairs) + 1) Mod 2 <> 0 Then
Err.Raise 5, "Inject", "Invalid parameters: expecting key/value pairs, but received an odd number of arguments."
End If
Inject = source
' Replace {key} with the pairing value.
Dim index As Long
For index = LBound(keyValuePairs) To UBound(keyValuePairs) Step 2
Inject = Replace(Inject, "{" & keyValuePairs(index) & "}", keyValuePairs(index + 1), , , vbTextCompare)
Next index
End Function
Simple Example
Here is a simple example that shows how to implement it.
Private Sub testingInject()
Const name As String = "Robert"
Const age As String = 31
Debug.Print Inject("Hello, {name}! You are {age} years old!", "name", name, "age", age)
'~> Hello, Robert! You are 31 years old!
End Sub
Although this may add a few extra strings, in my opinion, this makes it much easier to read long strings.
See the same simple example using concatenation:
Debug.Print "Hello, " & name & "! You are " & age & " years old!"
Using Scripting.Dicitionary
Really, a Scripting.Dictionary would be perfect for this since they are nothing but key/value pairs. It would be a simple adjustment to my code above, just take in a Dictionary as the parameter and make sure the keys match.
Public Function Inject(ByVal source As String, ByVal data As Scripting.Dictionary) As String
Inject = source
Dim key As Variant
For Each key In data.Keys
Inject = Replace(Inject, "{" & key & "}", data(key))
Next key
End Function
Dictionary example
And the example of using it for dictionaries:
Private Sub testingInject()
Dim person As New Scripting.Dictionary
person("name") = "Robert"
person("age") = 31
Debug.Print Inject("Hello, {name}! You are {age} years old!", person)
'~> Hello, Robert! You are 31 years old!
End Sub
Additional Considerations
Collections sound like they would be nice as well, but there is no way of accessing the keys. It would probably get messier that way.
If using the Dictionary method you might create a simple factory function for easily creating Dictionaries. You can find an example of that on my Github Library Page.
To mimic function overloading to give you all the different ways you could create a main Inject function and run a select statement within that.
Here is all the code needed to do that if need be:
Public Function Inject(ByVal source As String, ParamArray data() As Variant) As String
Dim firstElement As Variant
assign firstElement, data(LBound(data))
Inject = InjectCharacters(source)
Select Case True
Case TypeName(firstElement) = "Dictionary"
Inject = InjectDictionary(Inject, firstElement)
Case InStr(source, "{0}") > 0
Inject = injectIndexes(Inject, CVar(data))
Case (UBound(data) - LBound(data) + 1) Mod 2 = 0
Inject = InjectKeyValuePairs(Inject, CVar(data))
Case Else
Err.Raise 5, "Inject", "Invalid parameters: expecting key/value pairs or Dictionary or an {0} element."
End Select
End Function
Private Function injectIndexes(ByVal source As String, ByVal data As Variant)
injectIndexes = source
Dim index As Long
For index = LBound(data) To UBound(data)
injectIndexes = Replace(injectIndexes, "{" & index & "}", data(index))
Next index
End Function
Private Function InjectKeyValuePairs(ByVal source As String, ByVal keyValuePairs As Variant)
InjectKeyValuePairs = source
Dim index As Long
For index = LBound(keyValuePairs) To UBound(keyValuePairs) Step 2
InjectKeyValuePairs = Replace(InjectKeyValuePairs, "{" & keyValuePairs(index) & "}", keyValuePairs(index + 1))
Next index
End Function
Private Function InjectDictionary(ByVal source As String, ByVal data As Scripting.Dictionary) As String
InjectDictionary = source
Dim key As Variant
For Each key In data.Keys
InjectDictionary = Replace(InjectDictionary, "{" & key & "}", data(key))
Next key
End Function
' QUICK TOOL TO EITHER SET OR LET DEPENDING ON IF ELEMENT IS AN OBJECT
Private Function assign(ByRef variable As Variant, ByVal value As Variant)
If IsObject(value) Then
Set variable = value
Else
Let variable = value
End If
End Function
End Function
Private Function InjectCharacters(ByVal source As String) As String
InjectCharacters = source
Dim keyValuePairs As Variant
keyValuePairs = Array("n", vbNewLine, "t", vbTab, "r", vbCr, "f", vbLf)
If (UBound(keyValuePairs) - LBound(keyValuePairs) + 1) Mod 2 <> 0 Then
Err.Raise 5, "Inject", "Invalid variable: expecting key/value pairs, but received an odd number of arguments."
End If
Dim RegEx As Object
Set RegEx = CreateObject("VBScript.RegExp")
RegEx.Global = True
' Replace is ran twice since it is possible for back to back patterns.
Dim index As Long
For index = LBound(keyValuePairs) To UBound(keyValuePairs) Step 2
RegEx.Pattern = "((?:^|[^\\])(?:\\{2})*)(?:\\" & keyValuePairs(index) & ")+"
InjectCharacters = RegEx.Replace(InjectCharacters, "$1" & keyValuePairs(index + 1))
InjectCharacters = RegEx.Replace(InjectCharacters, "$1" & keyValuePairs(index + 1))
Next index
End Function

Answer 4

I have a library function SPrintF() which should do what you need.
It replaces occurrences of %s in the supplied string with an extensible number of parameters, using VBA's ParamArray() feature.
Usage:
SPrintF("%s:%s", 1, 1) => "1:1"
SPrintF("Property %s added at %s on %s", "88 High St, Clapham", Time, Date) => ""Property 88 High St, Clapham added at 11:30:27 on 25/07/2019"
Function SprintF(strInput As String, ParamArray varSubstitutions() As Variant) As String
'Formatted string print: replaces all occurrences of %s in input with substitutions
Dim i As Long
Dim s As String
s = strInput
For i = 0 To UBound(varSubstitutions)
s = Replace(s, "%s", varSubstitutions(i), , 1)
Next
SprintF = s
End Function
Just to add as a footnote, the idea for this was inspired by the C language printf function.

Answer 5

I use a similar code to that of #natancodes except that I use regex to replace the occurances and allow the user to specifiy description for the placeholders. This is useful when you have a big table (like in Access) with many strings or translations so that you still know what each number means.
Function Format(ByVal Source As String, ParamArray Replacements() As Variant) As String
Dim Replacement As Variant
Dim i As Long
For i = 0 To UBound(Replacements)
Dim rx As New RegExp
With rx
.Pattern = "{" & i & "(?::(.+?))?}"
.IgnoreCase = True
.Global = True
End With
Select Case VarType(Replacements(i))
Case vbObject
If Replacements(i) Is Nothing Then
Dim Matches As MatchCollection
Set Matches = rx.Execute(Source)
If Matches.Count = 1 Then
Dim Items As SubMatches: Set Items = Matches(0).SubMatches
Dim Default As String: Default = Items(0)
Source = rx.Replace(Source, Default)
End If
End If
Case vbString
Source = rx.Replace(Source, CStr(Replacements(i)))
End Select
Next
Format = Source
End Function
Sub TestFormat()
Debug.Print Format("{0:Hi}, {1:space}!", Nothing, "World")
End Sub