返回信息流vehicle.h
class Vehicle
{
public:
virtual void start(void)const=0;
virtual Vehicle* copy(void)const=0;
virtual ~Vehicle() {}
};
class SurrogateVehicle
{
public:
SurrogateVehicle();
SurrogateVehicle(const Vehicle& vehi) ;
SurrogateVehicle(const SurrogateVehicle& sv );
SurrogateVehicle & operator=(const SurrogateVehicle& sv);
~SurrogateVehicle();
void start();
private:
Vehicle* vehicle;
};
class truck:public Vehicle
{
void start()const ;
truck* copy() const ;
};
class motocycle:public Vehicle
{
void start()const ;
motocycle* copy() const ;
};
vehicle.cpp
#include "vehicle.h"
#include <iostream>
SurrogateVehicle::SurrogateVehicle():vehicle(0)
{
}
SurrogateVehicle::SurrogateVehicle(const Vehicle& vehi):vehicle(vehi.copy())
{
//vehicle = vehi.copy();
std::cout<<"test ppp";
}
SurrogateVehicle::SurrogateVehicle(const SurrogateVehicle& sv ):vehicle(sv.vehicle?sv.vehicle->copy():0)
{
}
SurrogateVehicle& SurrogateVehicle::operator =(const SurrogateVehicle &sv)
{
if ( vehicle )
{
delete vehicle;
std::cout<<std::endl;
}
std::cout<<"test=";
vehicle = sv.vehicle?sv.vehicle->copy():0;
return *this;
}
void SurrogateVehicle::start()
{
vehicle->start();
}
SurrogateVehicle::~SurrogateVehicle()
{
if( vehicle)
{
delete vehicle;
}
}
truck* truck::copy()const
{
std::cout<<"truck construction"<<std::endl;
return new truck(*this);
}
void truck::start()const
{
std::cout<<"truck start"<<std::endl;
}
motocycle* motocycle::copy()const
{
std::cout<<"motocycle construction"<<std::endl;
return new motocycle(*this);
}
void motocycle::start()const
{
std::cout<<"motocycle start"<<std::endl;
}
main.cpp
#include "vehicle.h"
#include <iostream>
int main(int argc,char *argv[])
{
truck first;
motocycle second;
//SurrogateVehicle stop_part[100];
SurrogateVehicle test;
test = first ;
system("pause");
return true;
}
询问 在运行时
调用了两次copy函数
truck construction
test ppptest=truck construction
不明白为什么。
这是一条镜像帖。来源：北邮人论坛 / cpp / #42491同步于 2010/8/18
该镜像源已超过 30 天没有更新，可能在源站已被删除。
CPP机器人发帖
C++问题
baimushan
2010/8/18镜像同步1 回复
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1 条回复
赋值的时候应该是生成临时对象了
【 在 baimushan 的大作中提到: 】
: vehicle.h
: class Vehicle
: {
: ...................