Option Explicit and Variable Declarations | Decoding VBA

Goal

Enable Option Explicit and declare variables with meaningful types.

When to use this

Always. Production macros should fail fast when a variable name is misspelled.

Example

Add this at the top of every standard module:

Option Explicit

Sub CountFilledRows()
    Dim ws As Worksheet
    Dim lastRow As Long

    Set ws = ThisWorkbook.Worksheets("Data")
    lastRow = ws.Cells(ws.Rows.Count, "A").End(xlUp).Row

    MsgBox "Filled rows: " & lastRow
End Sub

Common mistakes

• Omitting Option Explicit and accidentally creating new Variant variables via typos.
• Using Variant when Long, String, or Worksheet is known.

Next up

Read and write cells with the Range object—without Select/Activate.

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