VBA join array elements to then pass as multiple parameters to function - vba

Question

[Update: The question has been formed so that the functions can be copied directly into a VBA module and tested by running the test_callback_loop_function_works_with_multiple_parameters method]
I am using the Application.Run function to dynamically call methods within my VBA. The idea is that this helper will save me looping through dictionaries throughout various functions/subs within my VBA. Instead I can just call the following helper which will do the looping for me:
Public Function user_func_dictionary_loop(Dictionary As Dictionary, _
MethodCallback As String, _
Optional Params As Variant) As Boolean
Dim Key As Variant
For Each Key In Dictionary
If IsMissing(Params) Then
Application.Run MethodCallback, Dictionary(Key)
Else
Application.Run MethodCallback, user_param_replace(Dictionary(Key), Params)
End If
Next Key
End Function
If no Parameters are supplied to the function then it simply runs the MethodCallback with the Dictionary's key value. If there are parameters then an additional step is triggered below:
Private Function user_param_replace(Item As Variant, Optional Params As Variant) As Variant
Dim i As Long
Dim strTest As String
Dim Output As Variant
Output = replace_dictionary_values(Item, Params)
If IsArray(Output) Then
ReDim Preserve Output(0 To UBound(Output))
user_param_replace = Join(Output, ",")
Exit Function
End If
user_param_replace = Output
End Function
Private Function replace_dictionary_values(Item As Variant, Optional Params As Variant) As Variant
Dim l As Long
Dim varTemp() As Variant
Dim Param_Item As Variant
l = 0
If IsMissing(Params) Or Not IsArray(Params) Then
replace_dictionary_values = Replace$(Params, "{D:Value}", Item)
Exit Function
Else
ReDim varTemp(0 To UBound(Params))
For Each Param_Item In Params
varTemp(l) = Replace$(Param_Item, "{D:Value}", Item)
l = l + 1
Next Param_Item
End If
replace_dictionary_values = varTemp
End Function
The steps above allow a user to pass in parameters which contain {D:Value} which will then be replaced with the Dictionary's key value.
I've made a small unit test below with the idea that it should test the functionality of my method. At present I'm getting an "Argument not optional" error:
Function test_callback_loop_function_works_with_multiple_parameters() As Boolean
Dim dictTest As New Dictionary
dictTest.Add 1, "1 - Foo"
dictTest.Add 2, "2 - Foo"
dictTest.Add 3, "3 - Foo"
Dim MyArray(0 To 1) As Variant
MyArray(0) = "{D:Value}"
MyArray(1) = "Bar"
user_func_dictionary_loop dictTest, "custom_debug_print_multiple_params", MyArray
test_callback_loop_function_works_with_multiple_parameters = True
End Function
Function custom_debug_print_multiple_params(strPrint As String, strPrint2 As String) As String
Debug.Print strPrint & strPrint2
End Function
The output should be:
1 - FooBar
2 - FooBar
3 - FooBar
But I'm getting an
Run-time error '449' - Argument not optional
error on the Application.Run MethodCallback, user_param_replace(Dictionary(Key), Params) line.
My hunch is that because I'm trying to join array elements together with a "," to then pass through as parameters (in the Join(Output, ",") line) to the method, it's causing the test to fail.
So my question is, within VBA, is it possible to join the elements of an array together so they can then be passed, dynamically, to another method/function?

Answer 1

There is a problem with this line of code.
replace_dictionary_values = Replace$(Params, "{D:Value}", Item)
This line is called when IsMissing(Params) = True and, predictably, returns an error.
I also found that your test procedure can't work.
Function custom_debug_print_multiple_params(strPrint As String, strPrint2 As String) As String
Debug.Print strPrint & strPrint2
End Function
All your variables are variants but the two parameters of the above function are of string type. The arguments should be declared ByVal if variants of string type are to be passed. I recommend to test each function individually and make sure that it works before using its return value as parameters for other functions.
I suspect that part of your problem may be caused by your rather indiscriminate use of variants. For example, the Replace function you invoke in the faulty line quoted above requires 3 strings as arguments. In your code, both Item and Params (if it would exist) are variants. There is a good chance that your plan could actually work, but when something doesn't quite work, as is the case here, all those corners that were cut will have to be checked, adding more time to the debugging effort than could be saved during coding.
In the first example below the calling procedure supplies the two strings required by the called procedure. Variants of string type are passed which are converted to strings by the ByVal argument.
Function Test_TestPrint() As Boolean
Dim dictTest As New Scripting.Dictionary
Dim MyArray(0 To 1) As Variant
dictTest.Add 1, "1 - Foo"
dictTest.Add 2, "2 - Foo"
dictTest.Add 3, "3 - Foo"
MyArray(0) = "{D:Value}"
MyArray(1) = "Bar"
TestPrint MyArray(0), MyArray(1)
' user_func_dictionary_loop dictTest, "TestPrint", MyArray
Test_TestPrint = True
End Function
Sub TestPrint(ByVal strPrint As String, ByVal strPrint2 As String)
Debug.Print strPrint & strPrint2
End Sub
In the code below the array is passed to the executing procedure which expects such an array and prints out its elements.
Function Test_TestPrint2() As Boolean
Dim dictTest As New Scripting.Dictionary
Dim MyArray(0 To 1) As Variant
dictTest.Add 1, "1 - Foo"
dictTest.Add 2, "2 - Foo"
dictTest.Add 3, "3 - Foo"
MyArray(0) = "{D:Value}"
MyArray(1) = "Bar"
Sub TestPrint2 MyArray
' user_func_dictionary_loop dictTest, "TestPrint", MyArray
Test_TestPrint2 = True
End Function