Delphi ActiveX

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

Delphi ActiveX

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Integer;
subject: WideString;
pattern: WideString;
sb: TChilkatStringBuilder;
json: TChilkatJsonObject;
timeoutMs: Integer;
numMatches: Integer;

begin
success := 0;

subject := 'John Smith';
pattern := '(?<first>\\w+)\\s+(?<last>\\w+)';

sb := TChilkatStringBuilder.Create(Self);
sb.Append(subject);

json := TChilkatJsonObject.Create(Self);
json.EmitCompact := 0;

timeoutMs := 2000;
numMatches := sb.RegexMatch(pattern,json.ControlInterface,timeoutMs);
if (numMatches < 0) then
  begin
    // Probably an error in the regular expression.
    // Suggestion: Use AI to help create and/or diagnose regular expressions.
    Memo1.Lines.Add(sb.LastErrorText);
    Exit;
  end;

// Examine the matches:
Memo1.Lines.Add(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');
Memo1.Lines.Add('first: ' + json.StringOf('match[0].group[i].cap'));

json.I := json.IntOf('named.last');
Memo1.Lines.Add('last: ' + json.StringOf('match[0].group[i].cap'));

// Output is: 

// first: John
// last: Smith
end;