B4X Requires Chilkat v11.1.0+

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

B4X

Dim success As Boolean = False

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

Dim sb As ChilkatStringBuilder
sb.Initialize
sb.Append(subject)

Dim json As ChilkatJsonObject
json.Initialize
json.EmitCompact = False

Dim timeoutMs As Int = 2000
Dim numMatches As Int = 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.
    Log(sb.LastErrorText)
    Return
End If


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

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

'  Output is: 

'  first: John
'  last: Smith