C++ example using our API

Our API uses GraphQL, below is an example of how to leverage GraphQL’s automatic code generation to work with our services as if it were part of your application itself.

1. Start a new project and install dependencies

   Create project Setup vcpkg in the example

   #!/bin/bash
   mkdir example && cd example

2. Setup vcpkg & install dependencies

   Create the vcpkg.json file:

   ./vcpkg.json

   {
     "name": "example",
     "version-string": "0.0.1",
     "builtin-baseline": "095a29ce59608465032c3747307dd0009b3e089c",
     "dependencies": [
       {
         "name": "pegtl",
         "version>=": "3.2.8"
       },
       {
         "name": "cppgraphqlgen",
         "version>=": "4.5.7",
         "features": ["clientgen", "rapidjson"]
       },
       {
         "name": "boost-json",
         "version>=": "1.88.0"
       },
       {
         "name": "cpr",
         "version>=": "1.11.2"
       }
     ]
   }

   And then setup / install:

   git submodule add https://github.com/microsoft/vcpkg
   ./vcpkg/bootstrap-vcpkg.sh
   ./vcpkg/vcpkg install

3. Create a graphql file to query data

   You choose what data you want to fetch

   ./queries/Materials.graphql

   query ListMaterials($page: Int, $pageSize: Int, $filters: [MaterialFilter!]) {
     materials(page: $page, pageSize: $pageSize, filters: $filters) {
       pages
       pageInfo {
         hasPreviousPage
         hasNextPage
       }
       objects {
         ... on Material {
           id
           name
           brand {
             id
             name
           }
         }
       }
     }
   }

4. Autogenerate the code

   clientgen allows us to autogenerated all of the functions, structs and enums needed to handle our query files. This means we don’t need to write any manual requests with possible incorrect types, just call the function as if it were part of the library itself.

   mkdir -p ./generated/src
   mkdir -p ./generated/include
   curl https://api.helioadditive.com/graphql/scehma -o schema.graphqls
   ./vcpkg/packages/cppgraphqlgen_arm64-osx/tools/cppgraphqlgen/clientgen \
       --schema ./schema.graphqls \
       --request queries/Materials.graphql \
       --namespace HelioAdditive \
       --prefix Materials \
       --source-dir ./generated/src \
       --header-dir ./generated/include

5. Create the main.cpp app entrypoint

   All of the structs, enums and functions to handle all types to/from our API are already autogenerated including the serialization logic. This means you can now write interact with our API with 100% type confidence.

   ./src/main.cpp

   #include <iostream>
   #include <string>
   
   #include "MaterialsClient.h"
   #include "graphqlservice/GraphQLResponse.h"
   #include "graphqlservice/JSONResponse.h"
   
   namespace Materials = graphql::client::query::Materials;
   
   int main() {
       const std::string query = Materials::GetRequestText();
       graphql::response::Value variables = Materials::serializeVariables(Materials::Variables{.pageSize = 20, .page = 1});
       auto parsed_response = Materials::parseResponse(sendHttpRequest(query, variables));
   
       for (const auto &material : parsed_response.materials.objects) {
           std::cout << "Material ID: " << material.id.c_str() << ", Name: " << material.name << '\n';
       }
   
       return 0;
   }

   NOTE: C++ autogenerated GraphQL code does not include logic to handle the HTTP requests like in other languages, as such an example function of how to handle the HTTP requests is shown below with cpr, but one could easily use boost or libcurl based on what is used in your project:

   #include <cpr/cpr.h>
   #include <boost/json.hpp>
   
   graphql::response::Value sendHttpRequest(const std::string &query, graphql::response::Value &variables) {
       std::string body = boost::json::serialize(boost::json::object{
           {"query", query},
           {"variables", boost::json::parse(graphql::response::toJSON(std::move(variables))).as_object()}
       });
       return graphql::response::parseJSON(boost::json::serialize(boost::json::parse(
           cpr::Post(
               cpr::Url{"https://api.helioadditive.com/graphql"},
               cpr::Header{{"Content-Type", "application/json"}, {"Authorization", "Bearer <pat_token>"}},
               cpr::Body{body}
           ).text
       ).as_object()["data"].as_object()));
   }

6. Build

   C++ is an advanced language and every build system is different. For below example shows how one could use CMake to build:

   cmake_minimum_required(VERSION 3.14)
   project(ExampleApp)
   set(CMAKE_CXX_STANDARD 20)
   set(CMAKE_CXX_FLAGS "-std=c++20 -O3 ")
   
   include_directories(${VCPKG_DIR}/include)
   link_directories(${VCPKG_DIR}/lib)
   
   FIND_PACKAGE(CURL)
   find_package(Boost REQUIRED COMPONENTS json)
   find_package(cppgraphqlgen 4.5.7 CONFIG REQUIRED)
   find_package(cpr 1.11.1 REQUIRED)
   
   include_directories(generated/include)
   file(GLOB_RECURSE GENERATED_SRC "generated/src/*.cpp")
   file(GLOB_RECURSE GENERATED_HEADERS "generated/include/*.h")
   
   add_executable(ExampleApp src/main.cpp ${GENERATED_SRC})
   include_directories({CURL_INCLUDE_DIRS})
   target_link_libraries(ExampleApp
       PRIVATE
       cppgraphqlgen::graphqlservice
       cppgraphqlgen::graphqlclient
       cppgraphqlgen::graphqlresponse
       cppgraphqlgen::graphqlpeg
       cppgraphqlgen::graphqlcoro
       cppgraphqlgen::graphqljson
       taocpp::pegtl
       cpr::cpr
       Boost::json
   )
   target_include_directories(ExampleApp
       PUBLIC
       $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/generated>
       $<INSTALL_INTERFACE:generated/include>
       PRIVATE
       ${VCPKG_DIR}/include
   )