Pascal (Lazarus/Delphi)

Regular Expression with Multiple Matches and Named Capture Groups

See more Regular Expressions Examples

Demonstrates regular expressions with named capture groups and multiple matches. Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.JsonObject,
  Chilkat.StringBuilder;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  sb: TStringBuilder;
  crlf: Boolean;
  pattern: string;
  json: TJsonObject;
  timeoutMs: Integer;
  numMatches: Integer;
  idx_first: Integer;
  idx_last: Integer;
  i: Integer;
  matchCount: Integer;

begin
  success := False;

  sb := TStringBuilder.Create;
  crlf := True;
  sb.AppendLine('Name: John Smith',crlf);
  sb.AppendLine('Name: Jack Johnson',crlf);
  sb.AppendLine('Name: Mary Adams',crlf);

  WriteLn(sb.GetAsString());

  //  We have the following string:
  //  Name: John Smith
  //  Name: Jack Johnson
  //  Name: Mary Adams

  pattern := 'Name:\\s+(?<first>\\w+)\\s+(?<last>\\w+)';
  json := TJsonObject.Create;
  json.EmitCompact := False;

  timeoutMs := 2000;
  numMatches := sb.RegexMatch(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.
      WriteLn(sb.LastErrorText);
      Exit;
    end;

  //  Examine the matches:
  WriteLn(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": "Name: John Smith",
  //            "idx": 0,
  //            "len": 16
  //          },
  //          {
  //            "cap": "John",
  //            "idx": 6,
  //            "len": 4
  //          },
  //          {
  //            "cap": "Smith",
  //            "idx": 11,
  //            "len": 5
  //          }
  //        ]
  //      },
  //      {
  //        "group": [
  //          {
  //            "cap": "Name: Jack Johnson",
  //            "idx": 18,
  //            "len": 18
  //          },
  //          {
  //            "cap": "Jack",
  //            "idx": 24,
  //            "len": 4
  //          },
  //          {
  //            "cap": "Johnson",
  //            "idx": 29,
  //            "len": 7
  //          }
  //        ]
  //      },
  //      {
  //        "group": [
  //          {
  //            "cap": "Name: Mary Adams",
  //            "idx": 38,
  //            "len": 16
  //          },
  //          {
  //            "cap": "Mary",
  //            "idx": 44,
  //            "len": 4
  //          },
  //          {
  //            "cap": "Adams",
  //            "idx": 49,
  //            "len": 5
  //          }
  //        ]
  //      }
  //    ]
  //  }

  //  The capture group index is obtained by looking up the name in the JSON result.
  //  For example:

  idx_first := json.IntOf('named.first');
  idx_last := json.IntOf('named.last');

  i := 0;
  matchCount := json.SizeOfArray('match');
  while i < matchCount do
    begin
      WriteLn('Match ' + i + 1 + ':');
      json.I := i;

      json.J := idx_first;
      WriteLn('first: ' + json.StringOf('match[i].group[j].cap'));

      json.J := idx_last;
      WriteLn('first: ' + json.StringOf('match[i].group[j].cap'));

      WriteLn('');
      i := i + 1;
    end;

  //  Output is: 

  //  Match 1:
  //  first: John
  //  first: Smith
  //  
  //  Match 2:
  //  first: Jack
  //  first: Johnson
  //  
  //  Match 3:
  //  first: Mary
  //  first: Adams


  sb.Free;
  json.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.