Xojo Plugin Requires Chilkat v11.1.0+

Regular Expression Replace Capture Groups

See more Regular Expressions Examples

Demonstrates replacing capture groups for a regular expression.

Note: Chilkat uses PCRE2. See PCRE2 Regular Expressions
Also see: PCRE2 Performance

Xojo Plugin

Dim success As Boolean
success = False

Dim subject As String
subject = "John Anders, +_+_+ Mary Robins $$$$"
Dim pattern As String
pattern = "(?<first>\w+)\s+(?<last>\w+)"

Dim sb As New Chilkat.StringBuilder
success = sb.Append(subject)

Dim json As New Chilkat.JsonObject
json.EmitCompact = False

Dim timeoutMs As Int32
timeoutMs = 2000
Dim numMatches As Int32
numMatches = sb.RegexMatch(pattern,json,timeoutMs)
If (numMatches < 0) Then
    //  Probably an error in the regular expression.
    //  Suggestion: Use AI to help create and/or diagnose regular expressions.
    System.DebugLog(sb.LastErrorText)
    Return
End If

//  Examine the matches:
System.DebugLog(json.Emit())

//  There are 2 matches:

//  {
//    "named": {
//      "first": 1,
//      "last": 2
//    },
//    "match": [
//      {
//        "group": [
//          {
//            "cap": "John Anders",
//            "idx": 0,
//            "len": 11
//          },
//          {
//            "cap": "John",
//            "idx": 0,
//            "len": 4
//          },
//          {
//            "cap": "Anders",
//            "idx": 5,
//            "len": 6
//          }
//        ]
//      },
//      {
//        "group": [
//          {
//            "cap": "Mary Robins",
//            "idx": 19,
//            "len": 11
//          },
//          {
//            "cap": "Mary",
//            "idx": 19,
//            "len": 4
//          },
//          {
//            "cap": "Robins",
//            "idx": 24,
//            "len": 6
//          }
//        ]
//      }
//    ]
//  }

//  To replace capture groups, write code to examine each capture group within
//  each match, and provide a replacement string.
//  Then call RegexReplace.

//  For example, let's capitalize the first names, and add append "on" to the last name.
//  After doing replacements, we should get:  JOHN Anderson, +_+_+ MARY Robinson $$$$

Dim firstNameIdx As Int32
firstNameIdx = json.IntOf("named.first")
Dim lastNameIdx As Int32
lastNameIdx = json.IntOf("named.last")

Dim sbTemp As New Chilkat.StringBuilder

Dim i As Int32
i = 0
numMatches = json.SizeOfArray("match")
While i < numMatches

    json.I = i

    //  The replacement string for the first name will be all uppercase.
    json.J = firstNameIdx
    sbTemp.Clear 
    success = json.StringOfSb("match[i].group[j].cap",sbTemp)
    success = sbTemp.ToUppercase()
    success = json.UpdateSb("match[i].group[j].rep",sbTemp)

    //  Append "on" to the last name.
    json.J = lastNameIdx
    sbTemp.Clear 
    success = json.StringOfSb("match[i].group[j].cap",sbTemp)
    success = sbTemp.Append("on")
    success = json.UpdateSb("match[i].group[j].rep",sbTemp)

    i = i + 1
Wend

//  The JSON now has replacement strings:
System.DebugLog(json.Emit())

//  {
//    "named": {
//      "first": 1,
//      "last": 2
//    },
//    "match": [
//      {
//        "group": [
//          {
//            "cap": "John Anders",
//            "idx": 0,
//            "len": 11
//          },
//          {
//            "cap": "John",
//            "idx": 0,
//            "len": 4,
//            "rep": "JOHN"
//          },
//          {
//            "cap": "Anders",
//            "idx": 5,
//            "len": 6,
//            "rep": "Anderson"
//          }
//        ]
//      },
//      {
//        "group": [
//          {
//            "cap": "Mary Robins",
//            "idx": 19,
//            "len": 11
//          },
//          {
//            "cap": "Mary",
//            "idx": 19,
//            "len": 4,
//            "rep": "MARY"
//          },
//          {
//            "cap": "Robins",
//            "idx": 24,
//            "len": 6,
//            "rep": "Robinson"
//          }
//        ]
//      }
//    ]
//  }

//  Call RegexReplace to update the StringBuilder with the replacements.
success = sb.RegexReplace(json)
If (success = False) Then
    System.DebugLog(sb.LastErrorText)
    Return
End If

System.DebugLog("Result after doing replacements:")
System.DebugLog(sb.GetAsString())

//  Result after doing replacements:
//  JOHN Anderson, +_+_+ MARY Robinson $$$$