Function in function with arrays - arrays

Question

I don't get what's false in my code. I searched the error the whole morning! So I hope you can help me.
First, here's the problem code (the names of the variables aren't their real names):
Sheets(sheet).Range(nameOfTheRange).FormulaR1C1 = _
functionReturningString(functionReturningStrArr( _
Range(nameOfAnotherRange).Value, AnInputWorkSheet, "colNameInInputSheet"))
So my description on that:
All functions work fine standing alone, but in combination there is always this error (Language: German):
Fehler beim Kompilieren:
Unverträglicher Typ: Datenfeld oder benutzerdefinierter Typ erwartet
functionReturningString is a function with the following parameters(strArr() as Variant) --> it returns a String like a bulletlist.
functionReturningStrArr(nameWhichISearchInSheet as String, dataSheet as Worksheet, dataColumn, as String) --> it returns a Variant() for the bulletListing
I'm not sure if the second method really works so here's the code of it.
Function functionReturningStrArr(ByVal nameWhichISearchInSheet As String, ByVal datasheet As Worksheet, ByVal datacolumn As String) As String()
Dim returnArray() As String
Dim rowindex As Integer
Dim ID As String
Sheets(rawdataOverall).Cells(1, getColNumFromColName("Project")).EntireColumn.Select
'search correct dataset
For Each cell In Selection
If cell.Value = nameWhichISearchInSheet Then
rowindex = cell.row
Exit For
End If
Next cell
'get ID
ID = Sheets(rawdataOverall).Cells(rowindex, getColNumFromColName("ID")).Value
'search data from file with this ID
datasheet.Cells(1, getColNumFromColName(datacolumn)).EntireColumn.Select
Selection.UsedRange.Select
For Each cell In Selection
rowindex = cell.row
'check if row contains to this project
If Cells(rowindex, getColNumFromColName("ID")) = ID Then
ReDim Preserve returnArray(UBound(returnArray) + 1)
returnArray(UBound(returnArray)) = cell.Value
End If
Next cell
functionReturningStrArr = returnArray()
If you are asking yourselves what is getColNumFromColName, it is a method which works really fine, I used it in other projects too.

Answer 1

You really have to start declaring everything explicitly using Dim -- and force yourself to do this by writing Option Explicit at the top of your module. That way you will identify errors much more quickly.
Here
'get ID
ID = Sheets(rawdataOverall).Cells(rowindex, getcolnumformcolname("ID")).Value
you call a function called getcolnumformcolname; presumably form is a typo and you meant From as in getColNumFromColName. Had you had Option Explicit, you would have detected that error immediately.
The following three variables/arrays are not declared: rawdataOverall, cell, getDataFromThisProject. You should declare them and assign them a type explicitly.
Try fixing those things and see where that brings you.

Answer 2

Is seems a small portion of the function code snippet is wrong. on the very last line, you should assign the value of returnArray() to your function name like so:
functionReturningStrArr = returnArray()
Otherwise, you would need to extract the array from a variable named "getDataFromActualProject", as is shown in the example.
EDIT:
Alter your function "functionReturningStrArr As Variant" to return "As String()" instead of Variant. It seems you cant cast a Variant to a string array as you would expect.
EDIT:
I created a function to test this. This compile error shows up when you try to cast Variant as Array of string. This also includes a fix, your function that returns Variant MUST return array of string instead.
Sub RunTest()
Debug.Print getStringFromArray(getArray())
Debug.Print getStringFromArray(getVariant()) ' compile error! you cannot cast variant to array of string
End Sub
Function getArray() As String()
Dim returnArray(2) As String
returnArray(0) = "A"
returnArray(1) = "B"
returnArray(2) = "C"
getArray = returnArray()
End Function
Function getVariant() As Variant()
Dim returnArray(2) As String
returnArray(0) = "A"
returnArray(1) = "B"
returnArray(2) = "C"
getArray = returnArray() ' Not a compile error, you can cast string array to variant
End Function
Function getStringFromArray(inputArray() As String) As String
Dim returnString As String
For i = LBound(inputArray()) To UBound(inputArray())
If returnString = "" Then
returnString = inputArray(i)
Else
returnString = returnString & "," & inputArray(i)
End If
Next i
getStringFromArray = returnString
End Function