C ++这个指针总是const [英] C++ the this pointer is always const

问题描述

对于类X的非const成员函数，此指针的类型为X * const。

然后，成员函数的这个指针总是const。 / p>

然后，我们总是需要const转换为：

  void foo :: p（）{
 const_cast< int&> （member）= 1; 
} 
  

我缺少这里的东西吗？

解决方案

对于类X的非const成员函数，此指针的类型为X * const。

否，非常量成员函数中的 this 指针的类型只是 X * （它是一个右值）。但是，即使 都是 X * const ，仍然不会阻止您更改数据成员。

您的代码示例与您的问题不符。它显示了一个const成员函数。在const成员函数中， this 的类型是 const X * 。您不能更改const成员函数内的任何数据成员（除了声明为 mutable 的数据成员除外）。如果你的目标是更改数据成员，那么声明一个成员函数为 const 是一种矛盾。弥补你的心。

For a non const member function of class X, this pointer is of type X* const.

Then, this pointer for a member function is always const.

Then, do we always need to const cast as in:

void foo::p() {                        
      const_cast <int&> (member) = 1;    
}

Am I missing something here ?

解决方案

For a non const member function of class X, this pointer is of type X* const.

No, the type of the this pointer inside a non-const member function is just X* (and it is an rvalue). But even if this were X* const, that would still not prevent you from changing data members.

Your code example doesn't match your question. It shows a const member function. Inside a const member function, the type of this is const X*. You cannot change any data members inside a const member function (with the exception of data members declared as mutable). It is a contradiction to declare a member function as const if your goal is to change data members. Make up your mind.

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