DataFlex

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

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    String sSubject
    String sPattern
    Handle hoSb
    Variant vJson
    Handle hoJson
    Integer iTimeoutMs
    Integer iNumMatches
    String sTemp1
    Integer iTemp1

    Move False To iSuccess

    Move "John Smith" To sSubject
    Move "(?<first>\w+)\s+(?<last>\w+)" To sPattern

    Get Create (RefClass(cComChilkatStringBuilder)) To hoSb
    If (Not(IsComObjectCreated(hoSb))) Begin
        Send CreateComObject of hoSb
    End
    Get ComAppend Of hoSb sSubject To iSuccess

    Get Create (RefClass(cComChilkatJsonObject)) To hoJson
    If (Not(IsComObjectCreated(hoJson))) Begin
        Send CreateComObject of hoJson
    End
    Set ComEmitCompact Of hoJson To False

    Move 2000 To iTimeoutMs
    Get pvComObject of hoJson to vJson
    Get ComRegexMatch Of hoSb sPattern vJson iTimeoutMs To iNumMatches
    If (iNumMatches < 0) Begin
        // Probably an error in the regular expression.
        // Suggestion: Use AI to help create and/or diagnose regular expressions.
        Get ComLastErrorText Of hoSb To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Examine the matches:
    Get ComEmit Of hoJson To sTemp1
    Showln sTemp1

    // 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:

    Get ComIntOf Of hoJson "named.first" To iTemp1
    Set ComI Of hoJson To iTemp1
    Get ComStringOf Of hoJson "match[0].group[i].cap" To sTemp1
    Showln "first: " sTemp1

    Get ComIntOf Of hoJson "named.last" To iTemp1
    Set ComI Of hoJson To iTemp1
    Get ComStringOf Of hoJson "match[0].group[i].cap" To sTemp1
    Showln "last: " sTemp1

    // Output is: 

    // first: John
    // last: Smith


End_Procedure