Dart Requires Chilkat v11.5.0+

curl with Variable Substitution in a GraphQL Request Body

See more CURL Examples

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. Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // 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.
  final sbCurl = CkStringBuilder();
  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('}"');

  final curl = CkHttpCurl();

  // 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.
  final sbRawRequest = CkStringBuilder();
  try {
    curl.toRawRequest(sbCurl.getAsString(), sbRawRequest);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print(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
  //   }
  // }
}