指向引用的指针和指针的引用之间的差异 [英] Difference between pointer to a reference and reference to a pointer

问题描述

指向引用的指针，指向指针的指针和指向C ++中的指针的指针之间有什么区别？

What is the difference between pointer to a reference, reference to a pointer and pointer to a pointer in C++?

在哪里应该优先于另一个？ / p>

Where should one be preferred over the other?

推荐答案

首先，对指针的引用就像是对任何其他变量的引用：

First, a reference to a pointer is like a reference to any other variable:

void fun(int*& ref_to_ptr)
{
    ref_to_ptr = 0; // set the "passed" pointer to 0
    // if the pointer is not passed by ref,
    // then only the copy(parameter) you received is set to 0,
    // but the original pointer(outside the function) is not affected.
}

在C ++中，引用的指针是非法的，因为 - 引用只是一个概念，它允许程序员使别名的别名。指针是内存中的地方，具有其他地址，但引用不是。

A pointer to reference is illegal in C++, because -unlike a pointer- a reference is just a concept that allows the programmer to make aliases of something else. A pointer is a place in memory that has the address of something else, but a reference is NOT.

现在最后一个点可能不是水晶般清晰，如果你坚持处理引用作为指针。例如：

Now the last point might not be crystal clear, if you insist on dealing with references as pointers. e.g.:

int x;
int& rx = x; // from now on, rx is just like x.
// Unlike pointers, refs are not real objects in memory.
int* p = &x; // Ok
int* pr = ℞ // OK! but remember that rx is just x!
// i.e. rx is not something that exists alone, it has to refer to something else.
if( p == pr ) // true!
{ ... }

从上面的代码可以看出，引用，我们不处理与它所指的东西分开的东西。因此，引用的地址只是它所引用的地址。这就是为什么没有这样的东西称为地址的参考根据你在说什么。

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