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

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

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

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* 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;

success := 0;

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

// curl -X POST https://api.example.com/graphql \
//   -H "Content-Type: application/graphql; charset=utf-8" \
//   -H "Accept: application/json" \
//   --data-binary "mutation {
//   createUser(
//     input: {
//       name: \"{{name}}\"
//       city: \"{{city}}\"
//       note: \"{{note}}\"
//       bio: \"{{bio}}\"
//     }
//   ) {
//     id
//     name
//   }
// }"

// Build the above curl command.
sbCurl := TChilkatStringBuilder.Create(Self);
sbCurl.AppendLn('curl -X POST https://api.example.com/graphql \");
sbCurl.AppendLn('  -H "Content-Type: application/graphql; charset=utf-8" \");
sbCurl.AppendLn('  -H "Accept: application/json" \");
sbCurl.AppendLn('  -d "mutation {');
sbCurl.AppendLn('  createUser(');
sbCurl.AppendLn('    input: {');
sbCurl.AppendLn('      name: \\"{{name}}\\"');
sbCurl.AppendLn('      city: \\"{{city}}\\"');
sbCurl.AppendLn('      note: \\"{{note}}\\"');
sbCurl.AppendLn('      bio: \\"{{bio}}\\"');
sbCurl.AppendLn('    }');
sbCurl.AppendLn('  ) {');
sbCurl.AppendLn('    id');
sbCurl.AppendLn('    name');
sbCurl.AppendLn('  }');
sbCurl.AppendLn('}"');

curl := TChilkatHttpCurl.Create(Self);

// Provide values for variables
curl.SetVar('name','José O''Connor');
curl.SetVar('city','München');
curl.SetVar('note','He said "Hello, world!" — and left…');
curl.SetVar('bio','Loves sushi, café visits, and π ≈ 3.14159');

// 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 the quote chars around "Hello, world!" are properly escaped.

// POST /graphql HTTP/1.1
// Accept: application/json
// Host: api.example.com
// Content-Type: application/graphql; charset=utf-8
// Content-Length: 250
// 
// mutation {
//   createUser(
//     input: {
//       name: "José O'Connor"
//       city: "München"
//       note: "He said \"Hello, world!\" — and left…"
//       bio: "Loves sushi, café visits, and π ≈ 3.14159"
//     }
//   ) {
//     id
//     name
//   }
// }
end;