Subscript not in Range MS Access - vba

Question

I'm needing to get fields names from a query and put them into a dynamic array. I believe I have found the proper code this, however I get a "Subscript not in Range" error.
Code so far:
Dim qdf As QueryDef
Dim fld As Field
Dim o As Integer
Dim fieldCount as Integer
fieldCount = CurrentDb.QueryDefs("qryctAverage").Fields.Count
Set qdf = db.QueryDefs("qryctAverage")
Dim n As Integer
n = fieldCount
ReDim colHeaders(0 To n - 1)
For o = 0 To n - 1
colHeader(o) = qdf.Fields(o).Name
Next o
Line of error: colHeader(o) = qdf.Fields(o).Name
I'm fairly new to VBA so I appreciate the patience and time put in to helping out! Thanks in advance
Note: All answer I've found have applied to non-dynamic arrays.
EDIT:
I now get "Sub or Function not defined" after removing Dim colHeader() as String
Error Line: colHeader(o) = qdf.Fields(o).Name

Answer 1

Dim colHeader() As String
ReDim colHeaders(0 To n - 1)
You've declared colHeader, but resized colHeaders. Option Explicit can't pick that up, because the ReDim statement is perfectly valid as a declaration, too.
But then, colHeader isn't dimensioned, so index o is necessarily out of bounds:
colHeader(o) = qdf.Fields(o).Name
Change it to
colHeaders(o) = qfd.Fields(o).Name
I'd remove the Dim colHeader() As String declaration, and add Option Explicit at the top of the module if it's missing.

Answer 2

Another way would be to use a For Each block.
This code builds a single string of field names separated by an |.
Split is then used to turn the field string into an array of field names which is passed back to the calling procedure.
Option Explicit
Sub Test()
Dim colHeaders As Variant
colHeaders = FieldNames("qryctAverage")
Debug.Assert False 'Pause code so you can look at colHeaders.
End Sub
Public Function FieldNames(QueryName As String) As Variant
Dim qdf As DAO.QueryDef
Dim fld As DAO.Field
Dim fldNames As String
Set qdf = CurrentDb.QueryDefs(QueryName)
For Each fld In qdf.Fields
fldNames = fldNames & fld.Name & "|"
Next fld
fldNames = Left(fldNames, Len(fldNames) - 1)
FieldNames = Split(fldNames, "|")
End Function