VB.NET

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

VB.NET

Dim success As Boolean = False

Dim subject As String = "John Smith"
Dim pattern As String = "(?<first>\w+)\s+(?<last>\w+)"

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

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

Dim timeoutMs As Integer = 2000
Dim numMatches As Integer = 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.
    Debug.WriteLine(sb.LastErrorText)
    Exit Sub
End If


' Examine the matches:
Debug.WriteLine(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")
Debug.WriteLine("first: " & json.StringOf("match[0].group[i].cap"))

json.I = json.IntOf("named.last")
Debug.WriteLine("last: " & json.StringOf("match[0].group[i].cap"))

' Output is: 

' first: John
' last: Smith