Xojo Plugin

Regular Expression with Named Capture Groups

See more Regular Expressions Examples

Demonstrates regular expressions with named capture groups.

See the sample code below.

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

In PCRE2, named capture groups allow you to assign a name to a capturing group, making it easier to reference by name instead of number.

Syntax

(?<name>pattern)

or

(?'name'pattern)

Example

(?<first>\w+)\s+(?<last>\w+)

Applied to:

"John Smith"

Produces:

• first: John
• last: Smith

Xojo Plugin

Dim success As Boolean
success = False

Dim subject As String
subject = "John Smith"
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())

// Here is the JSON showing the matches.
// Important:  Capture group 0 always contains the entire match — that is, the portion of the input string that matches the full regular expression.

// {
//   "named": {
//     "first": 1,
//     "last": 2
//   },
//   "match": [
//     {
//       "group": [
//         {
//           "cap": "John Smith",
//           "idx": 0,
//           "len": 10
//         },
//         {
//           "cap": "John",
//           "idx": 0,
//           "len": 4
//         },
//         {
//           "cap": "Smith",
//           "idx": 5,
//           "len": 5
//         }
//       ]
//     }
//   ]
// }

// The capture group index is obtained by looking up the name in the JSON result.
// For example:

json.I = json.IntOf("named.first")
System.DebugLog("first: " + json.StringOf("match[0].group[i].cap"))

json.I = json.IntOf("named.last")
System.DebugLog("last: " + json.StringOf("match[0].group[i].cap"))

// Output is: 

// first: John
// last: Smith