Delphi ActiveX

Regular Expression Replace Capture Groups

See more Regular Expressions Examples

Demonstrates replacing capture groups for a regular expression.

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

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;
firstNameIdx: Integer;
lastNameIdx: Integer;
sbTemp: TChilkatStringBuilder;
i: Integer;

begin
success := 0;

subject := 'John Anders, +_+_+ Mary Robins $$$$';
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());

// There are 2 matches:

// {
//   "named": {
//     "first": 1,
//     "last": 2
//   },
//   "match": [
//     {
//       "group": [
//         {
//           "cap": "John Anders",
//           "idx": 0,
//           "len": 11
//         },
//         {
//           "cap": "John",
//           "idx": 0,
//           "len": 4
//         },
//         {
//           "cap": "Anders",
//           "idx": 5,
//           "len": 6
//         }
//       ]
//     },
//     {
//       "group": [
//         {
//           "cap": "Mary Robins",
//           "idx": 19,
//           "len": 11
//         },
//         {
//           "cap": "Mary",
//           "idx": 19,
//           "len": 4
//         },
//         {
//           "cap": "Robins",
//           "idx": 24,
//           "len": 6
//         }
//       ]
//     }
//   ]
// }

// To replace capture groups, write code to examine each capture group within
// each match, and provide a replacement string.
// Then call RegexReplace.

// For example, let's capitalize the first names, and add append "on" to the last name.
// After doing replacements, we should get:  JOHN Anderson, +_+_+ MARY Robinson $$$$

firstNameIdx := json.IntOf('named.first');
lastNameIdx := json.IntOf('named.last');

sbTemp := TChilkatStringBuilder.Create(Self);

i := 0;
numMatches := json.SizeOfArray('match');
while i < numMatches do
  begin

    json.I := i;

    // The replacement string for the first name will be all uppercase.
    json.J := firstNameIdx;
    sbTemp.Clear();
    json.StringOfSb('match[i].group[j].cap',sbTemp.ControlInterface);
    sbTemp.ToUppercase();
    json.UpdateSb('match[i].group[j].rep',sbTemp.ControlInterface);

    // Append "on" to the last name.
    json.J := lastNameIdx;
    sbTemp.Clear();
    json.StringOfSb('match[i].group[j].cap',sbTemp.ControlInterface);
    sbTemp.Append('on');
    json.UpdateSb('match[i].group[j].rep',sbTemp.ControlInterface);

    i := i + 1;
  end;

// The JSON now has replacement strings:
Memo1.Lines.Add(json.Emit());

// {
//   "named": {
//     "first": 1,
//     "last": 2
//   },
//   "match": [
//     {
//       "group": [
//         {
//           "cap": "John Anders",
//           "idx": 0,
//           "len": 11
//         },
//         {
//           "cap": "John",
//           "idx": 0,
//           "len": 4,
//           "rep": "JOHN"
//         },
//         {
//           "cap": "Anders",
//           "idx": 5,
//           "len": 6,
//           "rep": "Anderson"
//         }
//       ]
//     },
//     {
//       "group": [
//         {
//           "cap": "Mary Robins",
//           "idx": 19,
//           "len": 11
//         },
//         {
//           "cap": "Mary",
//           "idx": 19,
//           "len": 4,
//           "rep": "MARY"
//         },
//         {
//           "cap": "Robins",
//           "idx": 24,
//           "len": 6,
//           "rep": "Robinson"
//         }
//       ]
//     }
//   ]
// }

// Call RegexReplace to update the StringBuilder with the replacements.
success := sb.RegexReplace(json.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(sb.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('Result after doing replacements:');
Memo1.Lines.Add(sb.GetAsString());

// Result after doing replacements:
// JOHN Anderson, +_+_+ MARY Robinson $$$$
end;