(Objective-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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#import <CkoStringBuilder.h>
#import <CkoHttpCurl.h>

BOOL success = NO;

success = NO;

// 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.
CkoStringBuilder *sbCurl = [[CkoStringBuilder alloc] init];
[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: @"}\""];

CkoHttpCurl *curl = [[CkoHttpCurl alloc] init];

// Provide values for variables
[curl SetVar: @"name" varValue: @"José O'Connor"];
[curl SetVar: @"city" varValue: @"München"];
[curl SetVar: @"note" varValue: @"He said \"Hello, world!\" — and left…"];
[curl SetVar: @"bio" varValue: @"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.
CkoStringBuilder *sbRawRequest = [[CkoStringBuilder alloc] init];
success = [curl ToRawRequest: [sbCurl GetAsString] sb: sbRawRequest];
if (success == NO) {
    NSLog(@"%@",curl.LastErrorText);
    return;
}

NSLog(@"%@",[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
//   }
// }