VBA, search in column for specific character, extract string upto that character

Question

In a specific column, I want to search for a specific character in cells...say \"(\" or \"/\". Once this character is found in a cell, I want to extract the part from the be

Answer 1

This question is well suited for regular expressions. The following function returns the position of the character preceding the first match of a simple regex pattern in a given string. If no match is found, the function returns the length of the string. The function can be combined with the LEFT function to extract the text preceding the match. (The use of LEFT is necessary because, for the sake of simplicity, this function does not implement submatches.)

The following formula would extract the product names in your sample data:

  =LEFT(A1,regexmatch(A1," \(|\/| -| \*"))

Breaking down the match pattern " \(|\/| -| \*":

  " \("  matches a space followed by a left parenthesis 
         [the backslash escapes the "(", a special character in regular expressions] 

  "|"    signifies an alternative pattern to match

  "\/"   matches a forward slash (/)

  " -"   matches a space followed by a dash (-)

  " \*"  matches a space followed by an asterisk (*).

To learn more about regular expressions, see this regular expression tutorial, one of many available on the web.

In order for the function to work, you will need to set a reference to Microsoft VBScript Regular Expressions 5.5. To do this, select Tools/References from the VBA IDE and check this item, which will be well down the long list of references.

  Function regexMatch(text As String, rePattern As String)
      'Response to SO post 16591260
      'Adapted from code at http://www.macrostash.com/2011/10/08/
      '    simple-regular-expression-tutorial-for-excel-vba/.

      Dim regEx As New VBScript_RegExp_55.RegExp
      Dim matches As Variant

      regEx.pattern = rePattern
      regEx.IgnoreCase = True 'True to ignore case
      regEx.Global = False    'Return just the first match

      If regEx.Test(text) Then
         Set matches = regEx.Execute(text)
         regexMatch = matches(0).FirstIndex
      Else
         regexMatch = Len(text)
      End If

  End Function 

The following subroutine applies the string extraction to each cell in a specified data column and writes the new string to a specified result column. Although it would be possible to just call the function for each cell in the data column, this would incur the overhead of compiling the regular expression (which applies to all cells) each time the function was called. To avoid this overhead, the subroutine splits the match function in to two parts, with the pattern definition outside the loop through the data cells, and the pattern execution inside the loop.

  Sub SubRegexMatch()
      'Response to SO post 16591260
      'Extracts from string content of each data cell in a specified source
      '   column of the active worksheet the characters to the left of the first
      '   match of a regular expression, and writes the new string to corresponding
      '   rows in a specified result column.
      'Set the regular expression, source column, result column, and first
      '   data row in the "parameters" section
      'Regex match code was adapted from http://www.macrostash.com/2011/10/08/
      '   simple-regular-expression-tutorial-for-excel-vba/

      Dim regEx As New VBScript_RegExp_55.RegExp, _
          matches As Variant, _
          regexMatch As Long     'position of character *just before* match
      Dim srcCol As String, _
          resCol As String
      Dim srcRng As Range, _
          resRng As Range
      Dim firstRow As Long, _
          lastRow As Long
      Dim srcArr As Variant, _
          resArr() As String
      Dim i As Long

      'parameters
      regEx.Pattern = " \(|\/| -| \*"    'regular expression to be matched
      regEx.IgnoreCase = True
      regEx.Global = False               'return only the first match found
      srcCol = "A"                       'source data column
      resCol = "B"                       'result column
      firstRow = 2                       'set to first row with data

      With ActiveSheet
          lastRow = .Cells(Cells.Rows.Count, srcCol).End(xlUp).Row
          Set srcRng = .Range(srcCol & firstRow & ":" & srcCol & lastRow)
          Set resRng = .Range(resCol & firstRow & ":" & resCol & lastRow)
          srcArr = srcRng
          ReDim resArr(1 To lastRow - firstRow + 1)
          For i = 1 To srcRng.Rows.Count
              If regEx.Test(srcArr(i, 1)) Then
                  Set matches = regEx.Execute(srcArr(i, 1))
                  regexMatch = matches(0).FirstIndex
              Else
                  regexMatch = Len(srcArr(i, 1)) 'return length of original string if no match
              End If
              resArr(i) = Left(srcArr(i, 1), regexMatch)
          Next i
          resRng = WorksheetFunction.Transpose(resArr) 'assign result to worksheet
      End With
  End Sub