(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 <C_CkStringBuilderW.h>
#include <C_CkHttpCurlW.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkStringBuilderW sbCurl;
    HCkHttpCurlW curl;
    HCkStringBuilderW sbRawRequest;

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

    curl = CkHttpCurlW_Create();

    // Provide values for variables
    CkHttpCurlW_SetVar(curl,L"name",L"José O'Connor");
    CkHttpCurlW_SetVar(curl,L"city",L"München");
    CkHttpCurlW_SetVar(curl,L"note",L"He said \"Hello, world!\" — and left…");
    CkHttpCurlW_SetVar(curl,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.
    sbRawRequest = CkStringBuilderW_Create();
    success = CkHttpCurlW_ToRawRequest(curl,CkStringBuilderW_getAsString(sbCurl),sbRawRequest);
    if (success == FALSE) {
        wprintf(L"%s\n",CkHttpCurlW_lastErrorText(curl));
        CkStringBuilderW_Dispose(sbCurl);
        CkHttpCurlW_Dispose(curl);
        CkStringBuilderW_Dispose(sbRawRequest);
        return;
    }

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


    CkStringBuilderW_Dispose(sbCurl);
    CkHttpCurlW_Dispose(curl);
    CkStringBuilderW_Dispose(sbRawRequest);

    }