成员类型如何实现？ [英] How are member types implemented?

问题描述

我正在查看此资源：

http ：//www.cplusplus.com/reference/vector/vector/

例如，类上的迭代器成员类型向量。

For example, the iterator member type on class vector.

是否将成员类型简单地实现为typedef或向量类中的类似对象？对我来说，成员类型的实际含义还不清楚，我看过几本C ++教科书，他们甚至根本没有提到这个短语。

Would a "member type" simply be implemented as a typedef or something similar in the vector class? It is not clear to me what "member type" actually means, and I've looked at a couple C++ textbooks, they don't even mention this phrase at all.

推荐答案

C ++标准也不使用此短语。取而代之的是，它称其为嵌套类型名称（§9.9）。

The C++ Standard does not use this phrase either. Instead, it would call it a nested type name (§9.9).

有四种获取方法：

class C
{
public:
   typedef int int_type;       // as a nested typedef-name
   using float_type = float;   // C++11: typedef-name declared using 'using'

   class inner_type { /*...*/ };   // as a nested class or struct

   enum enum_type { one, two, three };  // nested enum (or 'enum class' in C++11)
};

嵌套的类型名称是在类范围内定义的，为了从该范围之外引用它们，必须提供姓名资格：

Nested type names are defined in class scope, and in order to refer to them from outside that scope, name qualification is required:

int_type     a1;          // error, 'int_type' not known
C::int_type  a2;          // OK
C::enum_type a3 = C::one; // OK

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