继承的典型问题
可能的重复：
为什么在 C++ 中不允许这样做？
为什么会这样C++ 中不允许...??
class base
{
private:
public:
void func()
{
cout<<"base";
}
};
class derived : private base
{
private:
public:
void func()
{
cout<<"derived";
}
};
int main()
{
base * ptr;
ptr = new derived;
((derived *)ptr)->func();
return 0;
}
我收到错误
**61 C:\Dev-Cpp\My Projects\pointertest.cpp `base' is an inaccessible base of `derived'**
我的问题是，由于 func() 在派生类中定义了 public 且语句 ((派生 *)ptr)->func();正在尝试显示派生的 func() ..为什么由于继承模式而存在可访问问题..虽然我已经有了公共派生函数，但继承模式（私有）如何影响调用() 在派生类中..？
如果继承模式更改为公共，我会得到我想要的结果..但是 func() 在基类中是私有的（因此基类的 func() 不会被继承）并且 func() 在派生模式中是公共的继承是公共为什么我仍然得到我想要的结果..我应该像前面的情况一样收到编译错误吗？
我完全困惑了..请告诉我编译器在这种情况下是如何工作的..??
Possible Duplicate:
Why is this not allowed in C++?
Why is this not allowed in C++...??
class base
{
private:
public:
void func()
{
cout<<"base";
}
};
class derived : private base
{
private:
public:
void func()
{
cout<<"derived";
}
};
int main()
{
base * ptr;
ptr = new derived;
((derived *)ptr)->func();
return 0;
}
I am getting an error
**61 C:\Dev-Cpp\My Projects\pointertest.cpp `base' is an inaccessible base of `derived'**
My question is that since func() is defined public in derived class and the statement
((derived *)ptr)->func(); is trying to display the func() of derived..Why is there an accessible issue due to mode of inheritance..How does mode of inheritance(private) affects the call although I already have public derived func() in derived class..?
If mode of inheritance is changed to public I get my desired result..But a case where func() is private in base(so as func() of base is not inherited) and also func() is public in derived and mode of inheritance is public why still am I getting my desired result..Shouldn I be getting an Compile error as in the previous case ??
I am totally confused ..Please tell me how the compiler works in this case..??
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当存在私有继承时，不能让基指针指向派生对象。
公共继承表达了一种isa关系。另一方面，私有继承表示根据关系实现
编译错误指的是以下行：
ptr = 新派生；You can't let the base pointer point to the derived object when there is private inheritance.
Public inheritance expresses an isa relationship. Private inheritance on the other hand expresses a implemented in terms of relationship
Ther compile error refers to the line:
ptr = new derived;