(Unicode C++) 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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#include <CkStringBuilderW.h>
#include <CkHttpCurlW.h>

void ChilkatSample(void)
    {
    bool 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.
    CkStringBuilderW sbCurl;
    sbCurl.AppendLn(L"curl -X POST https://api.example.com/graphql \\");
    sbCurl.AppendLn(L"  -H \"Content-Type: application/graphql; charset=utf-8\" \\");
    sbCurl.AppendLn(L"  -H \"Accept: application/json\" \\");
    sbCurl.AppendLn(L"  -d \"mutation {");
    sbCurl.AppendLn(L"  createUser(");
    sbCurl.AppendLn(L"    input: {");
    sbCurl.AppendLn(L"      name: \\\"{{name}}\\\"");
    sbCurl.AppendLn(L"      city: \\\"{{city}}\\\"");
    sbCurl.AppendLn(L"      note: \\\"{{note}}\\\"");
    sbCurl.AppendLn(L"      bio: \\\"{{bio}}\\\"");
    sbCurl.AppendLn(L"    }");
    sbCurl.AppendLn(L"  ) {");
    sbCurl.AppendLn(L"    id");
    sbCurl.AppendLn(L"    name");
    sbCurl.AppendLn(L"  }");
    sbCurl.AppendLn(L"}\"");

    CkHttpCurlW curl;

    // Provide values for variables
    curl.SetVar(L"name",L"José O'Connor");
    curl.SetVar(L"city",L"München");
    curl.SetVar(L"note",L"He said \"Hello, world!\" — and left…");
    curl.SetVar(L"bio",L"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.
    CkStringBuilderW sbRawRequest;
    success = curl.ToRawRequest(sbCurl.getAsString(),sbRawRequest);
    if (success == false) {
        wprintf(L"%s\n",curl.lastErrorText());
        return;
    }

    wprintf(L"%s\n",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
    //   }
    // }
    }