为什么和何时值得使用指针指向指针?

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可能重复: 如何在C中使用指针?

Possible Duplicate: How do pointer to pointers work in C?

你好

尽管如此，我认为我已经通过了编程的新手阶段，但是我仍然有一些问题，我无法以某种方式找到它们的解释.是的，那里有很多方法"，但是几乎没有人解释为什么和/或何时使用一种技术.

Altough I think I passed the newbie phase in programming I still have some questions that somehow I can't find them explained. Yes, there are plenty of "how to"s overthere but almost always nobody explains why and/or when one technique is useful.

就我而言，我发现在某些情况下，C ++中使用了指向指针的指针.指向对象的指针不够吗?有哪些好处? 在什么地方或什么时候应该使用指向指针的指针?在这件事上，我感到有些迷茫.

In my case I have discovered that in some cases a pointer to a pointer is used in C++. Is not a pointer to an object enough? Which are the benefits? Where or when should be used a pointer to a pointer? I feel little bit desorientated in this matter.

我希望有经验的专家可以回答这个问题，希望其他没有经验的程序员也可以分享. ;-)

I hope time experienced expert could respond to this concerns that hopefully is shared by other no so experienced programers. ;-)

谢谢大家.

朱伦.

推荐答案

好吧，以某种方式很难回答这样一个普遍的问题.

Well, it is somehow hard to answer to such a general question.

C ++程序员的第一个答案肯定是:不要在C ++中使用指针！因为您有很多比指针更安全的方法来处理问题，所以您的目标之一就是首先避免出现问题:)

First answer of a C++ programmer will certainly be : Do not use pointers in C++ ! As you have a lot of safer ways to handle problems than pointers, one of your goal will be to avoid them in the first place :)

因此，在C ++中很少使用指向指针的指针.它们主要用在C中.首先，因为在C中，字符串是"char *"，所以当您需要指向C字符串的指针"时，您必须以"char **"结尾.其次，由于您在C中没有引用，因此当您需要具有修改指针或将指针作为输出值的函数时，就需要为指针参数提供指针.通常，您会在分配内存的函数中发现这一点，因为它们会为您提供指向已分配内存的指针.

So pointers to pointers are seldom used in C++. They are mainly used in C. First, because in C, strings are "char*" so when you need a "pointer to a C string" you end with a "char**". Second, as you do not have references in C, when you need to have a function that modify a pointer or that give a pointer as an output value, you need to give a pointer to a pointer parameter. You typically find that in functions that allocate memory, as they give you a pointer to the allocated memory.

如果采用C ++方式，请尝试避免使用指针，通常会有更好的方式.

If you go the C++ way, try to avoid pointers, you usually have better ways.

my2c