C++加载动态库的形式来实现封装

目录结构

└── test
    ├── CMakeLists.txt
    ├── base.h                            //设置接口
    ├── drive.cpp                        //具体实现
    └── main.cpp                        //ｔｅｓｔ

---

CMakeLists.txt

cmake_minimum_required (VERSION 2.8)
project (test)
set(CMAKE_CXX_STANDARD 11)
include_directories(./)
add_library(drive SHARED drive.cpp) #将实现添加为动态库
add_executable(test main.cpp) #将test生成可执行
target_link_libraries(test ${CMAKE_DL_LIBS}) #链接dl库

---

base.h

#ifndef BASE_H
#define BASE_H
#include <iostream>
#include <memory>
#include <dlfcn.h>
using namespace std;
 //宏用在drive.cpp中生成产生子类对象的函数
#define USE_MAPFUSION_PLUGIN(C) extern "C"{\
    shared_ptr<base> createInstance(){return shared_ptr<base>(new C());}}     
class base;
typedef shared_ptr<base> (*funcCreatClass)();
class base {
public:
    virtual void print() {cout << "base" << endl;}
    static shared_ptr<base> create(const string& plugin) {
        int realFlags = RTLD_LAZY|RTLD_GLOBAL;
        void* handle = dlopen(plugin.c_str(), realFlags);//打开库
        if (!handle) {
            const char* err = dlerror();
            cerr << "Can not open file " << plugin << "since " << err << endl;
            return shared_ptr<base>();
        }
        funcCreatClass createFunc = (funcCreatClass)dlsym(handle, "createInstance");  //加载库中生成子类对象的函数
        if(!createFunc) return shared_ptr<base>();
        else return createFunc();
    }
};
#endif // BASE_H

---

drive.cpp

#include "base.h"
using namespace std;
class drive : public base {
public:
    virtual void print() {cout << "drive" << endl;}
};
USE_MAPFUSION_PLUGIN(drive)                                            //展开base.h中的宏来生成产生子类对象的函数

---

main.cpp

#include "base.h"
using namespace std;
int main(int argc, char *argv[])
{
    shared_ptr<base> a = base::create("libdrive.so");
    a->print();
}

---

运行结果

$ mkdir build
$ cd build
$ camke ..
$ make
$ ./test
///输出
//drive