Delphi ActiveX Requires Chilkat v11.5.0+

curl with Variable Substitution in a JSON Request Body

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This example shows how to use variables inside a JSON request body using the {{variable_name}} syntax. When the HTTP request’s Content-Type indicates JSON, Chilkat automatically applies proper JSON escaping to each substituted value, ensuring the resulting JSON remains valid. Delphi ActiveX

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!\""}