GraphQL API in C++: Step-by-Step Tutorial with Practical Examples

Introduction: GraphQL and C++ — A Powerful Duo for Modern APIs

GraphQL is becoming the de facto standard for building flexible and efficient APIs. While most tutorials focus on JavaScript or Python, C++ remains indispensable for high-load systems, game servers, and embedded solutions. In this step-by-step guide, we will build a full-fledged GraphQL API in C++ from scratch, using the graphql-cpp library and the cpp-httplib server.

You will learn how to set up the environment, define a schema, implement resolvers, and run the server. All code examples can be immediately applied in real projects.

1. Environment Setup and Dependency Installation

For this project, we will need:

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• A compiler with C++17 support (GCC 8+, Clang 7+, MSVC 2019+)
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• CMake (version 3.14+)
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• The graphql-cpp library (GraphQL implementation)
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• The cpp-httplib library (HTTP server)
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• The vcpkg package manager (optional, but convenient)
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Installation via vcpkg

git clone https://github.com/Microsoft/vcpkg.git\ncd vcpkg\n./bootstrap-vcpkg.sh\n./vcpkg install graphql-cpp cpp-httplib nlohmann-json

Project Structure

graphql-cpp-api/\n├── CMakeLists.txt\n├── src/\n│   ├── main.cpp\n│   ├── schema.cpp\n│   ├── schema.h\n│   ├── resolvers.cpp\n│   └── resolvers.h\n└── vcpkg.json

CMakeLists.txt

cmake_minimum_required(VERSION 3.14)\nproject(GraphQLCppApi)\n\nset(CMAKE_CXX_STANDARD 17)\nset(CMAKE_CXX_STANDARD_REQUIRED ON)\n\nfind_package(graphql-cpp CONFIG REQUIRED)\nfind_package(cpp-httplib CONFIG REQUIRED)\nfind_package(nlohmann_json CONFIG REQUIRED)\n\nadd_executable(graphql_server\n    src/main.cpp\n    src/schema.cpp\n    src/resolvers.cpp\n)\n\ntarget_link_libraries(graphql_server\n    graphql-cpp::graphql-cpp\n    cpp-httplib::cpp-httplib\n    nlohmann_json::nlohmann_json\n)

Now everything is ready for writing code.

2. Defining the GraphQL Schema and Types

Let's start by creating a schema for a simple book management API. We will have Book and Author types, as well as queries and mutations.

schema.h

#ifndef SCHEMA_H\n#define SCHEMA_H\n\n#include <graphqlcpp/GraphQLSchema.h>\n\nstd::shared_ptr<graphql::GraphQLSchema> createSchema();\n\n#endif

schema.cpp

#include "schema.h"\n#include "resolvers.h"\n\nstd::shared_ptr<graphql::GraphQLSchema> createSchema() {\n    using namespace graphql;\n\n    // Author type\n    auto authorType = object_type("Author", {\n        field("id", int_type()),\n        field("name", string_type()),\n        field("books", list_type(int_type()))\n    });\n\n    // Book type\n    auto bookType = object_type("Book", {\n        field("id", int_type()),\n        field("title", string_type()),\n        field("authorId", int_type()),\n        field("year", int_type()),\n        field("genre", string_type())\n    });\n\n    // Query root\n    auto queryType = object_type("Query", {\n        field("books", list_type(bookType), {\n            argument("genre", string_type(), true)  // optional argument\n        }, resolveBooks),\n        field("book", bookType, {\n            argument("id", int_type(), false)       // required argument\n        }, resolveBookById),\n        field("authors", list_type(authorType), resolveAuthors)\n    });\n\n    // Mutation root\n    auto mutationType = object_type("Mutation", {\n        field("addBook", bookType, {\n            argument("title", string_type(), false),\n            argument("authorId", int_type(), false),\n            argument("year", int_type(), false),\n            argument("genre", string_type(), false)\n        }, resolveAddBook),\n        field("deleteBook", bool_type(), {\n            argument("id", int_type(), false)\n        }, res