c++ - 为什么可以取消引用 C++ 迭代器，尽管它不是指针？

Question

我正在阅读 C++ Primer 5th，遇到如下代码:

    string s("some string");
    if (s.begin() != s.end())
    {
      auto it = s.begin();   
      *it = toupper(*it);
    }

它从迭代器接收一个值到字符串s中的第一个字符；然后通过 toupper() 将其更改为大写。 it 是如何取消引用的？不应该只是一个char类型的变量而不是指针吗？

Answer 1

它 是一个 iterator :

In C++, an iterator is any object that, pointing to some element in a range of elements (such as an array or a container), has the ability to iterate through the elements of that range using a set of operators (at least, the increment (++) and dereference (*) operators).

The most obvious form of iterator is a pointer: A pointer can point to elements in an array, and can iterate through them using the increment operator (++). But other forms of iterators exist. For example, each container type (such as a vector) has a specific iterator type designed to iterate through its elements in an efficient way.

Notice that while a pointer is a form of iterator, not all iterators have the same functionality a pointer has; To distinguish between the requirements an iterator shall have for a specific algorithm, five different iterator categories exist:

由于迭代器是一个行为类似于指针的智能对象(最初指向字符串的开头 - 这是一个 container )，并迭代该容器，它 可以取消引用，如您的代码示例所示。因此，通常它 可以用作指针。

其中，在您的情况下，指针在字符串中的当前位置被分配给它在该位置是的大写等价物:

*it = toupper(*it);