Delphi DLL Requires Chilkat v11.5.0+

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. Delphi DLL

var
success: Boolean;
sbCurl: HCkStringBuilder;
curl: HCkHttpCurl;
sbRawRequest: HCkStringBuilder;

begin
success := False;

success := False;

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

curl := CkHttpCurl_Create();

//  Provide values for variables
CkHttpCurl_SetVar(curl,'name','José O''Connor');
CkHttpCurl_SetVar(curl,'city','München');
CkHttpCurl_SetVar(curl,'note','He said "Hello, world!" — and left…');
CkHttpCurl_SetVar(curl,'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 := CkStringBuilder_Create();
success := CkHttpCurl_ToRawRequest(curl,CkStringBuilder__getAsString(sbCurl),sbRawRequest);
if (success = False) then
  begin
    Memo1.Lines.Add(CkHttpCurl__lastErrorText(curl));
    Exit;
  end;

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

//  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
//    }
//  }

CkStringBuilder_Dispose(sbCurl);
CkHttpCurl_Dispose(curl);
CkStringBuilder_Dispose(sbRawRequest);