中科新闻网温江老城房价:mutable在C++里怎么用？
来源：百度文库 编辑：中科新闻网 时间：2024/05/06 03:52:08
简单说一下就好了，谢谢！
mutable member-variable-declaration;
This keyword can only be applied to non-static and non-const data members of a class. If a data member is declared mutable, then it is legal to assign a value to this data member from a const member function.
上面的引自MSDN
举个例子:
#include <iostream>
#include <iomanip>
using namespace std;
class C
{
public:
C(int i):m_Count(i){}
int incr() const//注意这里的const
{
return ++m_Count;
}
int decr() const
{
return --m_Count;
}
private:
mutable int m_Count;//你可以试着将这里的mutable去掉再编译试试
};
void main()
{
C c1(0),c2(10);
for(int tmp,i=0;i<10;i++)
{
tmp = c1.incr();
cout<<setw(tmp)<<setfill(' ')<<tmp<<endl;
tmp = c2.decr();
cout<<setw(tmp)<<setfill(' ')<<tmp<<endl;
}
}