VBA Function to Retrieve Characters from a String

This document outlines a VBA function designed to retrieve specific characters from a given string based on provided start position and length.

Function Overview

The function GetSubstring will:

• Accept a string, start position, and length as parameters.
• Return a substring if the inputs are valid.
• Handle various input validation checks to ensure robustness.

VBA Code Snippet

Function GetSubstring(ByVal inputString As String, ByVal startPos As Long, ByVal length As Long) As String
    ' This function retrieves a substring from the inputString starting at startPos 
    ' and of specified length. It returns an empty string if inputs are invalid.

    ' Validate input parameters
    If startPos < 1 Then
        GetSubstring = "Error: Start position must be >= 1."
        Exit Function
    End If
    
    If length < 0 Then
        GetSubstring = "Error: Length must be >= 0."
        Exit Function
    End If
    
    If startPos > Len(inputString) Then
        GetSubstring = "Error: Start position exceeds string length."
        Exit Function
    End If
    
    ' Calculate the actual end position of the substring
    Dim endPos As Long
    endPos = startPos + length - 1
    
    ' If end position exceeds the original string length, adjust it
    If endPos > Len(inputString) Then
        endPos = Len(inputString)
    End If
    
    ' Extract the substring and return it
    GetSubstring = Mid(inputString, startPos, endPos - startPos + 1)
End Function

Code Explanation

1. Function Declaration:

   • GetSubstring takes three parameters: inputString, startPos, and length.

2. Input Validation:

   • Checks if startPos is less than 1. If so, an error message is returned.
   • Ensures length is not negative.
   • Confirms that startPos does not exceed the string length.

3. End Position Calculation:

   • Calculates the actual endpoint of the substring. Adjusts it if necessary to avoid exceeding the original string length.

4. Substring Extraction:

   • Uses the Mid function to retrieve the substring and return it.

Usage Example

To use the GetSubstring function in your VBA code:

Sub ExampleUsage()
    Dim result As String
    Dim originalString As String
    originalString = "Enterprise DNA is a data analytics platform."
    
    ' Retrieve a substring starting from position 12 with a length of 3
    result = GetSubstring(originalString, 12, 3)
    
    ' Output: "DNA"
    Debug.Print "Retrieved Substring: " & result
End Sub

Explanation of Example

• The ExampleUsage subroutine demonstrates how to call the GetSubstring function.
• It specifies the original string, the start position (12) to start retrieving characters, and the desired length (3).
• The result will be printed to the debug console as "DNA".

Conclusion

This function is simple yet powerful for extracting substrings from larger strings. This modular approach allows for easy integration and reuse throughout your VBA projects. For further enhancement of your data analysis skills, consider exploring courses available on the Enterprise DNA Platform, which offers rich content for data professionals.