C++ typedef 类使用
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C++ typedef class use
提问by kiriloff
Why use a typedef class {} Name?
为什么使用typedef class {} Name?
I learnt this in IBM C++ doc, no hint to use here.
我在IBM C++ doc中学到了这一点，这里没有提示。
回答by user93353
This is a hangover from the 'C' language.
这是'C'语言的后遗症。
In C, if you have
在 C 中，如果你有
struct Pt { int x; int y; };
then to declare a variable of this struct, you need to do
然后要声明这个结构的变量，你需要做
struct Pt p;
The typedef helped you avoid this in C
typedef 帮助您在 C 中避免这种情况
typedef struct { int x; int y; } Pt;
Now you can do
现在你可以做
Pt p;
in C.
在 C。
In C++, this was never necessary because
在 C++ 中，这从来没有必要，因为
class Pt { int x; int y; };
allowed you to do
允许你做
Pt p;
It provides no notational benefits in C++ as it does in C. OTOH, it leads to restrictions because this syntax does not provide any mechanism for construction, or destruction.
它在 C++ 中没有像在 C. OTOH 中那样提供符号上的好处，它会导致限制，因为这种语法不提供任何构造或销毁机制。
i.e. you cannot use the name typedef name in the constructor or destructor.
即您不能在构造函数或析构函数中使用名称 typedef 名称。
typedef class { int x; int y; } Pt;
You cannot have a constructor called Pt, nor a destructor. So in essence, most of the time, you shouldn't do this in C++.
你不能有一个叫做 Pt 的构造函数，也不能有一个析构函数。所以本质上，大多数时候，你不应该在 C++ 中这样做。
回答by Steve Jessop
This answer assumes that there's some interesting content in the class, not just {}.
这个答案假设课堂上有一些有趣的内容，而不仅仅是{}.
In C++, you can have a function with the same name as a class (for compatibility with C), but you pretty much never want to.
在 C++ 中，您可以拥有与类同名的函数（为了与 C 兼容），但您几乎永远不想这样做。
You can't have a function with the same name as a typedef, so doing this protects you against ill-disciplined name choices. Pretty much nobody bothers, and even if you're going to bother you'd probably write it:
您不能拥有与 typedef 同名的函数，因此这样做可以保护您免受不规范的名称选择。几乎没有人会打扰，即使您要打扰，您也可能会这样写：
class Name {};
typedef Name Name; // reserve the name
If the code you're referring to really is as written (I can't see it by following your link), then it's rather like class Name {};(which is a peculiar thing to write, why would you call an empty class Name?), but modified for the above consideration.
如果你所指的代码真的是这样写的（我无法通过你的链接看到它），那么它就像class Name {};（这是一个奇怪的东西，你为什么要调用一个空类Name？），但是修改了出于上述考虑。
