我正在尝试编译并运行这个程序。显然,它不起作用!我的问题是为什么从 bottom** 到 lefta** 的转换无效,而 bottom* 可以转换为 lefta* ?
#include<iostream>
using namespace std;
class top
{
private:
int a;
public:
top(int b):a(b){}
virtual void output(){cout<<a<<endl;}
};
class lefta:virtual public top
{
private:
int b;
public:
lefta(int c,int d):top(c),b(d){}
void output(){cout<<b<<endl;}
};
class righta:virtual public top
{
private:
int c;
public:
righta(int c,int d):top(c),c(d){}
void output(){cout<<c<<endl;}
};
class bottom:public lefta,public righta
{
private:
int d;
public:
bottom(int e,int f,int g,int h):top(e),lefta(e,f),righta(e,g),d(h){}
void output(){cout<<d<<endl;}
};
int main()
{
bottom* bo=new bottom(1,2,3,4);
// lefta* le=bo;
// le->output();
bottom** p_bo=&bo;//here
lefta** p_le=p_bo;//here
(*p_le)->output();
return 0;
}
最佳答案
class leftb : public lefta { /* blah */ };
bottom* bo = new bottom(1,2,3,4);
bottom** p_bo = &bo;
lefta** p_le = p_bo;// let's pretend it works
// now p_le points to the variable bo, which is of type bottom*
// so *p_le is a reference to the variable bo
*p_le = new leftb(1,2); // wait, did we just assign a leftb* to a bottom*?
// (and yeah, I'm leaking memory. Sue me)
// bo now points to a leftb, but it is a bottom*
// oops, we just broke the type system
关于c++ - 错误 : invalid conversion from 'bottom**' to 'lefta**' ,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/9397462/