Pascal (Lazarus/Delphi)

curl with Variable Substitution in the Request Body

See more CURL Examples

This example demonstrates using variables located in the request body with the {{variable_name}} syntax. 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.HttpCurl,
  Chilkat.StringBuilder;

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

procedure RunDemo;
var
  success: Boolean;
  sbCurl: TStringBuilder;
  curl: THttpCurl;
  sbRawRequest: TStringBuilder;

begin
  success := False;

  //  Variables can also be used within the HTTP request body.
  //  Variable names are enclosed between {{ and }}

  //  Here is a curl command with two variables {{name}} and {{age}} located in the data.

  //  curl -X POST https://api.example.com/data \
  //    -H "Content-Type: application/json" \
  //    -d '{"name":"{{name}}","age":{{age}}}'

  sbCurl := TStringBuilder.Create;
  sbCurl.AppendLn('curl -X POST https://api.example.com/data \");
  sbCurl.AppendLn('  -H "Content-Type: application/json" \");
  sbCurl.AppendLn('  -d ''{"name":"{{name}}","age":{{age}}}''');

  curl := THttpCurl.Create;

  //  Provide values for variables.
  curl.SetVar('name','Alice');
  curl.SetVar('age','30');

  //  To demonstrate how the variables are replaced, this example does not execute the curl command. 
  //  Instead, it generates the raw HTTP request that would be sent if the curl command were run.
  sbRawRequest := TStringBuilder.Create;
  success := curl.ToRawRequest(sbCurl.GetAsString(),sbRawRequest);
  if (success = False) then
    begin
      WriteLn(curl.LastErrorText);
      Exit;
    end;

  WriteLn(sbRawRequest.GetAsString());

  //  Output:

  //  POST /data HTTP/1.1
  //  Host: api.example.com
  //  Content-Type: application/json
  //  Content-Length: 25
  //  
  //  {"name":"Alice","age":30}

  //  --------------------------------------------------------------------------------------------------
  //  Note: Variable substitution in the request body can be turned off by 
  //  setting the EnableBodyVars property equal to False

  curl.EnableBodyVars := False;

  success := curl.ToRawRequest(sbCurl.GetAsString(),sbRawRequest);
  if (success = False) then
    begin
      WriteLn(curl.LastErrorText);
      Exit;
    end;

  WriteLn(sbRawRequest.GetAsString());

  //  The raw request with body variable substitution disable:

  //  Host: api.example.com
  //  Content-Type: application/json
  //  Content-Length: 33
  //  
  //  {"name":"{{name}}","age":{{age}}}


  sbCurl.Free;
  curl.Free;
  sbRawRequest.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.