Delphi DLL

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 DLL

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
subject: PWideChar;
pattern: PWideChar;
sb: HCkStringBuilder;
json: HCkJsonObject;
timeoutMs: Integer;
numMatches: Integer;
firstNameIdx: Integer;
lastNameIdx: Integer;
sbTemp: HCkStringBuilder;
i: Integer;

begin
success := False;

subject := 'John Anders, +_+_+ Mary Robins $$$$';
pattern := '(?<first>\\w+)\\s+(?<last>\\w+)';

sb := CkStringBuilder_Create();
CkStringBuilder_Append(sb,subject);

json := CkJsonObject_Create();
CkJsonObject_putEmitCompact(json,False);

timeoutMs := 2000;
numMatches := CkStringBuilder_RegexMatch(sb,pattern,json,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(CkStringBuilder__lastErrorText(sb));
    Exit;
  end;

// Examine the matches:
Memo1.Lines.Add(CkJsonObject__emit(json));

// 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 := CkJsonObject_IntOf(json,'named.first');
lastNameIdx := CkJsonObject_IntOf(json,'named.last');

sbTemp := CkStringBuilder_Create();

i := 0;
numMatches := CkJsonObject_SizeOfArray(json,'match');
while i < numMatches do
  begin

    CkJsonObject_putI(json,i);

    // The replacement string for the first name will be all uppercase.
    CkJsonObject_putJ(json,firstNameIdx);
    CkStringBuilder_Clear(sbTemp);
    CkJsonObject_StringOfSb(json,'match[i].group[j].cap',sbTemp);
    CkStringBuilder_ToUppercase(sbTemp);
    CkJsonObject_UpdateSb(json,'match[i].group[j].rep',sbTemp);

    // Append "on" to the last name.
    CkJsonObject_putJ(json,lastNameIdx);
    CkStringBuilder_Clear(sbTemp);
    CkJsonObject_StringOfSb(json,'match[i].group[j].cap',sbTemp);
    CkStringBuilder_Append(sbTemp,'on');
    CkJsonObject_UpdateSb(json,'match[i].group[j].rep',sbTemp);

    i := i + 1;
  end;

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

// {
//   "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 := CkStringBuilder_RegexReplace(sb,json);
if (success = False) then
  begin
    Memo1.Lines.Add(CkStringBuilder__lastErrorText(sb));
    Exit;
  end;

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

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

CkStringBuilder_Dispose(sb);
CkJsonObject_Dispose(json);
CkStringBuilder_Dispose(sbTemp);

end;