我试图对一个真正 const 的类进行 const 操作 - 它不会更改该类指向的数据。
例如:
class Node{
public:
int val;
};
class V{
public:
Node * node; //what is the change that is needed here?
void const_action()const{
node->val=5; //error wanted here
}
void action(){
node->val=5; //error is not wanted here
}
};
您可以使用模板来强制指针的 const 正确性,而无需更改类的含义或实现:
template <typename T>
class PreseveConstPointer
{
T *t_;
public:
PreseveConstPointer(T *t = nullptr)
: t_(t)
{
}
PreseveConstPointer<T> * operator=(T *t)
{
t_ = t;
return this;
}
T* operator->()
{
return t_;
}
T const * operator->() const
{
return t_;
}
T * data()
{
return t_;
}
};
class Node{
public:
int val;
};
class V{
public:
PreseveConstPointer<Node> node;
V()
{
node = new Node;
}
~V()
{
if(node.data())
delete node.data();
}
void const_action()const{
node->val=5; // You will get an error here
}
void action(){
node->val=5; // No error here
}
};
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