GraphQL API in C++: Complete Guide with Examples

GraphQL API with C++: Step-by-Step Tutorial

GraphQL is a powerful query language for APIs that allows clients to request exactly the data they need, and nothing extra. While C++ is not the most popular language for building web APIs, its performance and memory control make it an excellent choice for high-load systems. In this tutorial, we will create a working GraphQL server in C++ using the graphql-cpp library.

What You Need to Get Started

For this project, you will need:

• A compiler with C++17 support (GCC 8+, Clang 7+, MSVC 2019+)
• CMake version 3.14 or higher
• The graphql-cpp library (install via vcpkg or build from source)
• The libmicrohttpd library for the HTTP server

Install dependencies via vcpkg:

git clone https://github.com/microsoft/vcpkg.gitcd vcpkg./bootstrap-vcpkg.sh./vcpkg install graphql-cpp libmicrohttpd

Creating the Basic Project Structure

Let's start by setting up the CMake project. Create a CMakeLists.txt file:

cmake_minimum_required(VERSION 3.14)project(graphql-cpp-tutorial)

set(CMAKE_CXX_STANDARD 17)set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(graphql-cpp CONFIG REQUIRED)find_package(MHD CONFIG REQUIRED)

add_executable(graphql-server main.cpp)target_link_libraries(graphql-server     graphql-cpp::graphql-cpp    MHD::MHD)

Now create the main file main.cpp with a minimal server:

#include <graphql-cpp/GraphQL.h>#include <microhttpd.h>#include <iostream>#include <string>

using namespace graphql::cpp;

// HTTP request handler functionstatic enum MHD_Result request_handler(void* cls,    struct MHD_Connection* connection,    const char* url,    const char* method,    const char* version,    const char* upload_data,    size_t* upload_data_size,    void** con_cls) {        const char* response_str = "{\\"data\\":{\\"hello\\":\\"world\\"}}";    struct MHD_Response* response = MHD_create_response_from_buffer(        strlen(response_str),         (void*)response_str,         MHD_RESPMEM_PERSISTENT    );    MHD_add_response_header(response, "Content-Type", "application/json");    int ret = MHD_queue_response(connection, MHD_HTTP_OK, response);    MHD_destroy_response(response);    return ret == MHD_YES ? MHD_YES : MHD_NO;}

int main() {    struct MHD_Daemon* daemon = MHD_start_daemon(        MHD_USE_INTERNAL_POLLING_THREAD,        4000,        NULL, NULL,        &request_handler,        NULL,        MHD_OPTION_END    );        if (daemon == NULL) {        std::cerr << "Failed to start server" << std::endl;        return 1;    }        std::cout << "Server running on http://localhost:4000/graphql" << std::endl;    getchar();    MHD_stop_daemon(daemon);    return 0;}

Defining the GraphQL Schema

Now let's add a real GraphQL schema. We'll create a Book type and a root Query type:

#include <graphql-cpp/Schema.h>#include <graphql-cpp/Type.h>#include <vector>#include <memory>

using namespace graphql::cpp;

// Data modelstruct Book {    int id;    std::string title;    std::string author;    int year;};

// Book repository (simulating a database)class BookRepository {public:    static std::vector<Book> getAll() {        return {            {1, "War and Peace", "Leo Tolstoy", 1869},            {2, "Crime and Punishment", "Fyodor Dostoevsky", 1866},            {3, "The Master and Margarita", "Mikhail Bulgakov", 1967}        };    }        static Book getById(int id) {        auto books = getAll();        for (const auto& book