C

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. C

#include <C_CkStringBuilder.h>
#include <C_CkHttpCurl.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkStringBuilder sbCurl;
    HCkHttpCurl curl;
    HCkStringBuilder 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 = 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) {
        printf("%s\n",CkHttpCurl_lastErrorText(curl));
        CkStringBuilder_Dispose(sbCurl);
        CkHttpCurl_Dispose(curl);
        CkStringBuilder_Dispose(sbRawRequest);
        return;
    }

    printf("%s\n",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);

    }