Xojo Plugin

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 $$$$