1. The effect achieved
There are three different classes A, B, and C in the project. Select the class to execute through the configuration file. For example, configure CLASSNAME=A in the configuration file. When we get the CLASSNAME in the configuration, we can perform the method in class A.
2. Realize
2.1 Base class (base class that operates through polymorphism)
//F.h文件内容
#ifndef F_H
#define F_H
class F
{
public:
virtual void fun()=0;
};
#endif
2.2 Object mapping basic class (base class can also be used)
The following can be kept in a header file class.h
//基础类，可以使用基本类F代替
class ClassMappingObject
{
public:
virtual ~ClassMappingObject()=default;
virtual void classinit()=0; //为第二种宏定义提供初始化函数，可以没有
};
Type definition using functors
using RegisterFunc = std::function<std::unique_ptr<ClassMappingObject>()>;
inline std::map<std::string ,RegisterFunc> objectMap; //此为全局类的映射表;结构为{类名:类对象}
//在多个项目中可能会出现重复定义等错误，使用inline进行避免
function for registration
static void registerObject(const std::string& name,RegisterFunc func) {
//传入的进行类名和对象
objectMap[name] = func;
}
Get object by class name
template <typename T>
T* createObject(const std::string& name) {
if (objectMap.find(name) == objectMap.end()) {
return nullptr;
}
auto ptr = objectMap[name]();
// 从基类动态转换为外部需要的类型
return dynamic_cast<T*>(ptr.release());
}
Define macros for registration(1)
template <typename T1>
std::unique_ptr<ClassMappingObject> class_make_unique() {
auto* ptr = new T1;
return std::unique_ptr<ClassMappingObject>(dynamic_cast<ClassMappingObject*>(ptr));
}
#ifndef REGISTER_CLASS
#define REGISTER_CLASS(Type)\
static struct _ObjectRegisterTask##Type {
\
_ObjectRegisterTask##Type() {
\
registerObject(#Type,class_make_unique<Type>); \
}; \
} _task##Type; // NOLINT
#endif
Define macros for registration(2)
//第二种宏定义
struct RegisterTask {
RegisterTask( string a) {
std::cout<<a<<std::endl;
}
static string registerfun(const std::string& name,
std::function<std::unique_ptr<ClassMappingObject>()> func) {
registerObject(name,func);
return name;
}
};
#ifndef RegisterTask
#define RegisterTask(Type)\
static RegisterTask task##Type(RegisterTask::registerfun(#Type,class_make_unique<Type>));
#endif
The entire code of class.h
#ifndef CLASS_H
#define CLASS_H
#include<iostream>
#include<functional>
#include <memory>
#include <map>
#include <stdarg.h>
using namespace std;
class ClassMappingObject
{
public:
virtual void classinit()=0;
virtual ~ClassMappingObject()=default;
};
using RegisterFunc = std::function<std::unique_ptr<ClassMappingObject>()>;
inline std::map<std::string ,RegisterFunc> objectMap;
static void registerObject(const std::string& name,RegisterFunc func) {
objectMap[name] = func;
}
template <typename T>
T* createObject(const std::string& name) {
for(auto m: objectMap)
{
// std::cout<<"keys: "<<m.first<<std::endl;
}
if (objectMap.find(name) == objectMap.end()) {
return nullptr;
}
auto ptr = objectMap[name]();
// 从基类动态转换为外部需要的类型
return dynamic_cast<T*>(ptr.release());
}
//第一种宏定义
template <typename T1>
std::unique_ptr<ClassMappingObject> class_make_unique() {
auto* ptr = new T1;
return std::unique_ptr<ClassMappingObject>(dynamic_cast<ClassMappingObject*>(ptr));
}
#ifndef REGISTER_CLASS
#define REGISTER_CLASS(Type)\
static struct _ObjectRegisterTask##Type {
\
_ObjectRegisterTask##Type() {
\
registerObject(#Type,class_make_unique<Type>); \
}; \
} _task##Type; // NOLINT
#endif
//第二种宏定义
struct RegisterTask {
RegisterTask( string a) {
std::cout<<a<<std::endl;
}
static string registerfun(const std::string& name,
std::function<std::unique_ptr<ClassMappingObject>()> func) {
registerObject(name,func);
return name;
}
};
#ifndef REGISTER_CLASS_2
#define REGISTER_CLASS_2(Type)\
static RegisterTask task##Type(RegisterTask::registerfun(#Type,class_make_unique<Type>));
#endif
#endif
2.3 Per category
#include"class.h"
#include"F.h"
class Per:public F,public ClassMappingObject
{
public:
void classinit() //实现ClassMappingObject中函数进行初始化
{
tem=10;
std::cout<<"Per classinit"<<std::endl;
}
virtual void fun() //实现F中虚函数进行执行业务
{
std::cout<<"Per fun:"<<tem<<std::endl;
}
private:
int tem=0;
};
//进行注册
// REGISTER_CLASS(Per);
REGISTER_CLASS_2(Per)
2.4 Per1 class
#include"class.h"
#include"F.h"
class Per1:public F,public ClassMappingObject
{
public:
void classinit() //实现ClassMappingObject中函数进行初始化
{
tem=10;
std::cout<<"Per1 classinit"<<std::endl;
}
virtual void fun() //实现F中虚函数进行执行业务
{
std::cout<<"Per1 fun:"<<tem<<std::endl;
}
private:
int tem=0;
};
//进行注册
// REGISTER_CLASS(Per1);
REGISTER_CLASS_2(Per1);
2.5 Student class
#include"class.h"
#include<vector>
#include"F.h"
class Student :public F, public ClassMappingObject
{
public:
Student(int a=10){
tem = a;}
virtual void fun()
{
std::cout<<"Student fun"<<tem<<std::endl;
}
public:
void classinit()
{
tem=80;
std::cout<<"Student classinit"<<std::endl;
}
private:
float tem;
};
// REGISTER_CLASS(Student);
REGISTER_CLASS_2(Student);
3. Use
#include"classtet1.cpp"
#include"classtet2.cpp"
#include"classtet3.cpp"
#include"F.h"
int main(int argc, char const *argv[])
{
/* code */
F* ptr = createObject<F>("Per"); //获取基类类型，实现多态
ptr->fun();
return 0;
}