(Delphi ActiveX) curl with Variable Substitution in a JSON Request Body

See more CURL Examples

Note: This example requires Chilkat v11.5.0 or greater.

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

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;
sbCurl: TChilkatStringBuilder;
curl: TChilkatHttpCurl;
sbRawRequest: TChilkatStringBuilder;

begin
success := 0;

// Variable names are enclosed between {{ and }}
// Important: The variable {{var_name}} should be placed inside the quotes.

// This is correct:
// curl -X POST https://api.example.com/messages \
//   -H "Content-Type: application/json" \
//   -d '{"text":"{{message}}"}'

// This is incorrect:
//   -d '{"text":{{message}}}'

sbCurl := TChilkatStringBuilder.Create(Self);
sbCurl.AppendLn('curl -X POST https://api.example.com/messages \");
sbCurl.AppendLn('  -H "Content-Type: application/json" \");
sbCurl.AppendLn('  -d ''{"text":"{{message}}"}''');

curl := TChilkatHttpCurl.Create(Self);

// In this example, the value we'll provide for the "message" variable
// will contain chars that require JSON escaping.
curl.SetVar('message','He said "Hello, world!"');

// 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 := TChilkatStringBuilder.Create(Self);
success := curl.ToRawRequest(sbCurl.GetAsString(),sbRawRequest.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(curl.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add(sbRawRequest.GetAsString());

// The output is shown below.
// Notice that the quote chars around "Hello World!" are properly JSON escaped.

// POST /messages HTTP/1.1
// Host: api.example.com
// Content-Type: application/json
// Content-Length: 36
// 
// {"text":"He said \"Hello, world!\""}
end;