请教赋值拷贝

[Michael_Xie]

class Base
{
int* num;
...
};
class Derived : public Base
{
char* ch;
...
Derived& operator = ( const Derived& obj )
{
...//在这里我如何使得基类的num也拷贝了一份呢？
}
}

[gooderfeng]

base提供接口，然后调用base接口设置。
现在的程序子类不能访问父类的私有变量。

[Michael_Xie]

问题已经解决，即：
在Base中正确重载=,然后在Derived的操作符重载=中调用基类的=函数即可。
Base::operator = ( obj )。
谢谢大家的关注！

[hilary0810]

Derived& operator = ( const Derived& obj )
{
if (this != &obj)
memcpy(this,&obj,sizeof(Derived));
return *this
}

[kuike]

1楼的这个拷贝有问题，完全等同于默认的赋值拷贝，即采用位拷贝方式。num默认是private，所以派生类Drived无法访问父类的该私有成员。
class Base
{
int* num;
...
public:
Base& operator=(const Base& b)
{
if(this == &b)
return *this;
if(num)
delete num;
num = new int;
*num = *Base.num;
return *this;
}
};

class Derived : public Base
{
char* ch;
...
Derived& operator = ( const Derived& obj )
{
if(this == &obj) return *this;

//ÔÚÕâÀïÎÒÈçºÎʹµÃ»ùÀàµÄnumÒ²¿½±´ÁËÒ»·ÝÄØ£¿
CBase::operator=(const_cast(obj));
if(ch)
delete []ch;

ch = new char[strlen(obj.ch)+1];
strcpy(ch, obj.ch);

return *this;
}
}

[kuike]

中文注视没解析对