C++ 11使用可变长参数构建单例池

单一的单例有时很难满足需求，我们往往需要根据不同的规格，创建不同类型的单例实例。
本例实现满足上述需求的单例池。
代码目录如下，

图片.png

代码如下，
test/CMakeLists.txt

cmake_minimum_required(VERSION 2.6)

if(APPLE)
    message(STATUS "This is Apple, do nothing.")
    set(CMAKE_MACOSX_RPATH 1)
    set(CMAKE_PREFIX_PATH /Users/aabjfzhu/software/vcpkg/ports/cppwork/vcpkg_installed/x64-osx/share )
elseif(UNIX)
    message(STATUS "This is linux, set CMAKE_PREFIX_PATH.")
    set(CMAKE_PREFIX_PATH /vcpkg/ports/cppwork/vcpkg_installed/x64-linux/share)
endif(APPLE)

project(multiton)

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-narrowing")

add_definitions(-g)

find_package(ZLIB)

find_package(OpenCV REQUIRED )
find_package(Arrow CONFIG REQUIRED)

find_package(unofficial-brotli REQUIRED)
find_package(unofficial-utf8proc CONFIG REQUIRED)
find_package(Thrift CONFIG REQUIRED)

find_package(glog REQUIRED)

find_package(OpenSSL REQUIRED)

find_package(Boost REQUIRED COMPONENTS
    system
    filesystem
    serialization
    program_options
    thread
    )

find_package(DataFrame REQUIRED)

if(APPLE)
    MESSAGE(STATUS "This is APPLE, set INCLUDE_DIRS")
set(INCLUDE_DIRS ${Boost_INCLUDE_DIRS} /usr/local/include /usr/local/iODBC/include /opt/snowflake/snowflakeodbc/include/ ${CMAKE_CURRENT_SOURCE_DIR}/../include/ ${CMAKE_CURRENT_SOURCE_DIR}/../../../include)
elseif(UNIX)
    MESSAGE(STATUS "This is linux, set INCLUDE_DIRS")
    set(INCLUDE_DIRS ${Boost_INCLUDE_DIRS} /usr/local/include ${CMAKE_CURRENT_SOURCE_DIR}/../include/   ${CMAKE_CURRENT_SOURCE_DIR}/../../../include/)
endif(APPLE)


if(APPLE)
    MESSAGE(STATUS "This is APPLE, set LINK_DIRS")
    set(LINK_DIRS /usr/local/lib /usr/local/iODBC/lib /opt/snowflake/snowflakeodbc/lib/universal)
elseif(UNIX)
    MESSAGE(STATUS "This is linux, set LINK_DIRS")
    set(LINK_DIRS ${Boost_INCLUDE_DIRS} /usr/local/lib /vcpkg/ports/cppwork/vcpkg_installed/x64-linux/lib)
endif(APPLE)

if(APPLE)
    MESSAGE(STATUS "This is APPLE, set ODBC_LIBS")
    set(ODBC_LIBS iodbc iodbcinst)
elseif(UNIX)
    MESSAGE(STATUS "This is linux, set LINK_DIRS")
    set(ODBC_LIBS odbc odbcinst ltdl)
endif(APPLE)

include_directories(${INCLUDE_DIRS})
LINK_DIRECTORIES(${LINK_DIRS})

file( GLOB test_file_list ${CMAKE_CURRENT_SOURCE_DIR}/*.cpp) 

file( GLOB APP_SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/../impl/*.cpp ${CMAKE_CURRENT_SOURCE_DIR}/../include/*.h ${CMAKE_CURRENT_SOURCE_DIR}/../include/*.cpp ${CMAKE_CURRENT_SOURCE_DIR}/../../../include/arr_/impl/*.cpp ${CMAKE_CURRENT_SOURCE_DIR}/../../../include/http/impl/*.cpp ${CMAKE_CURRENT_SOURCE_DIR}/../../../include/yaml/impl/*.cpp ${CMAKE_CURRENT_SOURCE_DIR}/../../../include/df/impl/*.cpp ${CMAKE_CURRENT_SOURCE_DIR}/../../../include/death_handler/impl/*.cpp)

add_library(${PROJECT_NAME}_lib SHARED ${APP_SOURCES} ${test_file})
target_link_libraries(${PROJECT_NAME}_lib ${Boost_LIBRARIES} ZLIB::ZLIB glog::glog DataFrame::DataFrame ${OpenCV_LIBS})
target_link_libraries(${PROJECT_NAME}_lib OpenSSL::SSL OpenSSL::Crypto libgtest.a pystring libyaml-cpp.a libgmock.a ${ODBC_LIBS} libnanodbc.a pthread dl backtrace libzstd.a libbz2.a libsnappy.a re2::re2 parquet lz4 unofficial::brotli::brotlidec-static unofficial::brotli::brotlienc-static unofficial::brotli::brotlicommon-static utf8proc thrift::thrift  arrow arrow_dataset)

foreach( test_file ${test_file_list} )
    file(RELATIVE_PATH filename ${CMAKE_CURRENT_SOURCE_DIR} ${test_file})
    string(REPLACE ".cpp" "" file ${filename})
    add_executable(${file}  ${test_file})
    target_link_libraries(${file} ${PROJECT_NAME}_lib)
endforeach( test_file ${test_file_list})

test/multiton_test.cpp

#include "death_handler/death_handler.h"
#include 
#include "multiton.hpp"

#include 
#include 
#include "df/df.h"



int main(int argc, char** argv) {
    FLAGS_log_dir = "./";
    FLAGS_alsologtostderr = true;
    // 日志级别 INFO, WARNING, ERROR, FATAL 的值分别为0、1、2、3
    FLAGS_minloglevel = 0;

    Debug::DeathHandler dh;

    google::InitGoogleLogging("./logs.log");
    testing::InitGoogleTest(&argc, argv);
    int ret = RUN_ALL_TESTS();
    return ret;
}

GTEST_TEST(MultitonTests, Multiton) {
    auto main = MultitonPrinter::get(Importance::Primary);
    auto aux = MultitonPrinter::get(Importance::Secondary);
    auto aux2 = MultitonPrinter::get(Importance::Secondary);

    auto small = MultitonCircle::get(Size::Small);
    auto medium = MultitonCircle::get(Size::Medium, 2.0f);
    auto large = MultitonCircle::get(Size::Large, 3.0f);
}

include/multiton.hpp

#ifndef _FREDRIC_MULTITON_HPP_
#define _FREDRIC_MULTITON_HPP_

#include 
#include 
#include 
#include 

enum class Importance {
    Primary,
    Secondary,
    Tertiary
};

enum class Size {
    Large,
    Medium,
    Small
};

template 
class Multiton {
public:
    template
    static std::shared_ptr get(Key const& key, Args&& ... args) {
        if(auto const it = instances.find(key); it!=instances.end()) {
            return it->second;
        }

        auto instance = std::make_shared(std::forward(args)...);
        instances[key] = instance;
        return instance;
    }

private:
    static std::map> instances;

protected:
    Multiton() = default;
    virtual ~Multiton() = default;
};

template 
std::map> Multiton::instances{};

class Printer {
    static int totalInstanceCount;
public:
    Printer() {
        ++ Printer::totalInstanceCount;
        std::cout << "A total of " <<
            Printer::totalInstanceCount <<
            " instances created so far\n";
    }
};

int Printer::totalInstanceCount = 0;


class Circle {
    static int totalInstanceCount;
    float redius {1.0f};
public:
   
    Circle() {
        ++ Circle::totalInstanceCount;
        std::cout << "A total of " <<
            Circle::totalInstanceCount <<
            " circles created so far\n";
    }

    Circle(float redius_): redius {redius_} {
        ++ Circle::totalInstanceCount;
        std::cout << "A total of " <<
            Circle::totalInstanceCount <<
            " circles created so far\n";
    }
};

int Circle::totalInstanceCount = 0;


using MultitonPrinter = Multiton;
using MultitonCircle = Multiton;
#endif

程序输出如下，

图片.png

C++ 11使用可变长参数构建单例池

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