C++11手写责任链模式 - 更新英雄的属性值

本例实现手写责任链，进行英雄的属性值更新。链表部分使用手写单向链表的形式实现，使用的是尾插法。
程序代码结构如下，

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(pointer_chain)

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/pointer_chain_test.cpp

#include "death_handler/death_handler.h"
#include <glog/logging.h>
#include "pointer_chain.hpp"

#include "http/http_util.h"
#include <utility>
#include <gtest/gtest.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(PointerChainTests, PointerChainAllChain) {
   Creature goblin {"Goblin", 1, 1};
   CreatureModifer root{goblin};
   DoubleAttackModifier r1 {goblin};
   DoubleAttackModifier r1_2 {goblin};
   IncreaseDefenseModifer r2 {goblin};
   root.add(&r1);
   root.add(&r1_2);
   root.add(&r2);
   root.handle();
   std::cout << goblin << "\n"; 
} 

GTEST_TEST(PingPongSvcTests, PointerChainBreakChain) {
   Creature goblin {"Goblin", 1, 1};
   CreatureModifer root{goblin};
   NoBonusesModifier nm {goblin};
   DoubleAttackModifier r1 {goblin};
   DoubleAttackModifier r1_2 {goblin};
   IncreaseDefenseModifer r2 {goblin};
   // 从这里断开链接，啥都没发生
   root.add(&nm);
   root.add(&r1);
   root.add(&r1_2);
   root.add(&r2);
   root.handle();
   std::cout << goblin << "\n"; 
}

include/pointer_chain.hpp

#ifndef _FREDRIC_POINTER_CHAIN_HPP_
#define _FREDRIC_POINTER_CHAIN_HPP_

#include <string>
#include <iostream>
#include <sstream>
#include <vector>

struct Creature {
   std::string name;
   int attack, defense;

   Creature(std::string const& name_, int attack_, int defense_): name{name_}, attack{attack_}, defense{defense_} {

   }

   friend std::ostream& operator<<(std::ostream& os, Creature const& c) {
       os << "name: " << c.name << " attack: " << c.attack << " defense: " << c.defense;
       return os;
   }
};

class CreatureModifer {
   CreatureModifer* next{nullptr};
protected:
   Creature& creature;

public:
   CreatureModifer(Creature& creature_): creature{creature_} {}
   // 构建单向链表
   void add(CreatureModifer* cm) {
       if(next) next->add(cm);
       else next = cm;
   }

   // 直接调用next的handle方法，接起链条
   virtual void handle() {
       if(next) next->handle();
   }
};


class DoubleAttackModifier: public CreatureModifer {
public:
   DoubleAttackModifier(Creature& creature_): CreatureModifer(creature_) {}

   void handle() override {
       creature.attack *= 2;
       CreatureModifer::handle();
   }
};

class IncreaseDefenseModifer: public CreatureModifer {
public:
   IncreaseDefenseModifer(Creature& creature_): CreatureModifer(creature_) {}
   void handle() override {
       if(creature.attack <= 2) 
           ++ creature.defense;
       CreatureModifer::handle();
   }
};

class NoBonusesModifier: public CreatureModifer {
public:
   NoBonusesModifier(Creature& creature_): CreatureModifer(creature_) {}
   // 啥都不干，断开链接
   void handle() override {
   }
};

#endif

程序输出如下