const之陷阱注意

 1.常量不能为左值

cannot convert 'this' pointer from 'const class X' to 'class X &'

例子:

#include <iostream.h>
class X
{
   int i;
   public:
     void modify() {cout<<"haha"<<endl;}
};

const class X fun(){return X();}

void main()
{
 //fun().modify(); //常量不能为左值,所以下例也不成立:
 //error C2662: 'modify' : cannot convert 'this' pointer from 'const class X' to 'class X &'
 const X g = X();
 g.modify();
}

解决方案

void modify() const  {cout<<"haha"<<endl;}
2. 类常量成员初始化 (用初始化成员列表)

class Y{

public:

    const size;

        Y();

};

Y::Y():size(100){}

class X{

        enum{i=100};

};

 

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