# Naming Conventions
# Variable Names
Variables hold data. Name them after what they're used for, not after their data type or scope, using a noun. If you feel compelled to number your variables (e.g.
thing1, thing2, thing3), then consider using an appropriate data structure instead (e.g. an array, a
Collection, or a
Names of variables that represent an iteratable set of values - e.g. an array, a
Dictionary, or a
Range of cells, should be plural.
Some common VBA naming conventions go thus:
For procedure-level Variables:
Public Sub ExampleNaming(ByVal inputValue As Long, ByRef inputVariable As Long) Dim procedureVariable As Long Dim someOtherVariable As String End Sub
For module-level Variables:
Public GlobalVariable As Long Private ModuleVariable As String
SHOUTY_SNAKE_CASE is commonly used to differentiate constants from variables:
Public Const GLOBAL_CONSTANT As String = "Project Version #1.000.000.001" Private Const MODULE_CONSTANT As String = "Something relevant to this Module" Public Sub SomeProcedure() Const PROCEDURE_CONSTANT As Long = 10 End Sub
PascalCase names make cleaner-looking code and are just as good, given IntelliSense uses different icons for variables and constants:
# Hungarian Notation
Name them after what they're used for, not after their data type or scope.
"Hungarian Notation makes it easier to see what the type of a variable is"
If you write your code such as procedures adhere to the Single Responsibility Principle (as it should), you should never be looking at a screenful of variable declarations at the top of any procedure; declare variables as close as possible to their first usage, and their data type will always be in plain sight if you declare them with an explicit type. The VBE's Ctrl+i shortcut can be used to display a variable's type in a tooltip, too.
What a variable is used for is much more useful information than its data type, especially in a language such as VBA which happily and implicitly converts a type into another as needed.
strFile in this example:
Function bReadFile(ByVal strFile As String, ByRef strData As String) As Boolean Dim bRetVal As Boolean Dim iFile As Integer On Error GoTo CleanFail iFile = FreeFile Open strFile For Input As #iFile Input #iFile, strData bRetVal = True CleanExit: Close #iFile bReadFile = bRetVal Exit Function CleanFail: bRetVal = False Resume CleanExit End Function
Function CanReadFile(ByVal path As String, ByRef outContent As String) As Boolean On Error GoTo CleanFail Dim handle As Integer handle = FreeFile Open path For Input As #handle Input #handle, outContent Dim result As Boolean result = True CleanExit: Close #handle CanReadFile = result Exit Function CleanFail: result = False Resume CleanExit End Function
strData is passed
ByRef in the top example, but beside the fact that we're lucky enough to see that it's explicitly passed as such, there's no indication that
strData is actually returned by the function.
The bottom example names it
out prefix is what Hungarian Notation was invented for: to help clarify what a variable is used for, in this case to clearly identify it as an "out" parameter.
This is useful, because IntelliSense by itself doesn't display
ByRef, even when the parameter is explicitly passed by reference:
<img src="https://i.stack.imgur.com/3FAHc.png" alt="IntelliSense showing "CanReadFile(ByVal path As String, outComment As String) As Boolean" when the actual signature specifies outComment as explicitly passed by reference ("ByRef")" />
Which leads to...
Hungarian Done Right
Hungarian Notation originally didn't have anything to do with variable types (opens new window). In fact, Hungarian Notation done right is actually useful. Consider this small example (
As Integer removed for brevety):
Public Sub Copy(iX1, iY1, iX2, iY2) End Sub
Public Sub Copy(srcColumn, srcRow, dstColumn, dstRow) End Sub
dst are Hungarian Notation prefixes here, and they convey useful information that cannot otherwise already be inferred from the parameter names or IntelliSense showing us the declared type.
Of course there's a better way to convey it all, using proper abstraction and real words that can be pronounced out loud and make sense - as a contrived example:
Type Coordinate RowIndex As Long ColumnIndex As Long End Type Sub Copy(source As Coordinate, destination As Coordinate) End Sub
# Procedure Names
Procedures do something. Name them after what they're doing, using a verb. If accurately naming a procedure is not possible, likely the procedure is doing too many things and needs to be broken down into smaller, more specialized procedures.
Some common VBA naming conventions go thus:
For all Procedures:
Public Sub DoThing() End Sub Private Function ReturnSomeValue() As [DataType] End Function
For event handler procedures:
Public Sub Workbook_Open() End Sub Public Sub Button1_Click() End Sub
Event handlers are usually automatically named by the VBE; renaming them without renaming the object and/or the handled event will break the code - the code will run and compile, but the handler procedure will be orphaned and will never be executed.
Consider a Boolean-returning function:
Function bReadFile(ByVal strFile As String, ByRef strData As String) As Boolean End Function
Function CanReadFile(ByVal path As String, ByRef outContent As String) As Boolean End Function
Can prefix does serve the same purpose as the
b prefix: it identifies the function's return value as a
Can reads better than
If CanReadFile(path, content) Then
If bReadFile(strFile, strData) Then
Consider using prefixes such as
Has in front of Boolean-returning members (functions and properties), but only when it adds value. This conforms with the current Microsoft naming guidelines (opens new window).