什么是& **这完全返回？ [英] What does &**this return exactly?

问题描述

这是一个指向调用对象的指针（它返回r值）。

*这是一个指向调用对象的指针该地址的值）。

**这是一个指向调用对象（???）的指针的指针。

& ***这是对调用对象（???）的指针指针的引用。

  std :: vector< int> :: iterator i = vector1.begin（）; 
  

i是指向其自己的r值的指针（返回自己的值）。

* i是向量中包含的对象的r值的指针（返回指向& value的值）。

** i是指向包含在向量（???）中的对象的r值的指针。

我真的很困惑。

下面是一个示例代码，其中我们找到表达式& ** this：

 code> class _Iter 
 {
 private：
 ListElem * pCurr; 
 const List * pList; 
 
 public：
 _Iter（ListElem * pCurr，const List * list）
：pCurr_（pCurr），pList（list）
 {} 
 b $ b T& operator *（）{return pCurr _-> data; } 
 T * operator->（）{return& ** this; } 
}; 
  

解决方案

$ c>是指向当前对象的指针。

* this 是对当前对象的引用，即此已取消引用。





如果从<$ c返回的对象的值超过了 $ c> **此具有重载的运算符和（）函数，然后& ** this 计算返回值（** this）.operator&（）。否则，& **这个是指向重载的一元运算符* 当前对象。

示例：

  #include< iostream& 
 
 struct A 
 {
 int b; 
 int a; 
 int&运算符*（）{return a;} 
 
 int * test（）
 {
 return& ** this; 
} 
}; 
 
 int main（）
 {
 A a; 
 std :: cout<< Address of a.a：<< a.test（）< std :: endl; 
 std :: cout<< Address of a.a：<< &（* a）<< std :: endl; 
 std :: cout<< Address of a.a：<< &（a.a）< std :: endl; 
 return 0; 
} 
  

输出示例：

 地址aa：0x7fffbc200754 
地址aa：0x7fffbc200754 
地址aa：0x7fffbc200754 
  

this is a pointer to the calling object (it returns the r-value).

*this is a pointer to the pointer of the calling object (it returns the value of the address).

**this is a pointer to the pointer of the pointer of the calling object (???).

&***this is a reference to the pointer of the pointer of the pointer of the calling object (???).

std::vector<int>:: iterator i = vector1.begin();

i is the pointer to its own r-value (returns its own value).

*i is the pointer of a r-value of an object contained in a vector (returns the value pointed in &value).

**i is the pointer to the pointer of a r-value of an object contained in a vector (???).

I am really confused.

Here's a sample code where we find the expression &**this:

class _Iter
{
private:
    ListElem *pCurr;
    const List *pList;

public:
    _Iter(ListElem *pCurr, const List *list)
        : pCurr_(pCurr), pList(list)
    {}

    T& operator*() { return pCurr_->data; }
    T* operator->() { return &**this; }
};

解决方案

this is a pointer to the current object.

*this is a reference to the current object, i.e. this dereferenced.

**this is the returned value of the overloaded unary operator* function called on the current object.

If the object returned from **this has an overloaded operator&() function, then &**this evaluates to the returned value of (**this).operator&(). Otherwise, &**this is the pointer to the returned value of the overloaded unary operator* function called on the current object.

Example:

#include <iostream>

struct A
{
   int b;
   int a;
   int& operator*() {return a;}

   int* test()
   {
      return &**this;
   }
};

int main()
{
   A a;
   std::cout << "Address of a.a: " << a.test() << std::endl;
   std::cout << "Address of a.a: " << &(*a) << std::endl;
   std::cout << "Address of a.a: " << &(a.a) << std::endl;
   return 0;
}

Sample output:

Address of a.a: 0x7fffbc200754
Address of a.a: 0x7fffbc200754
Address of a.a: 0x7fffbc200754

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