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. Unicode C++

#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
    //    }
    //  }
    }