C++ - 结构与类
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C++ - struct vs. class
提问by Simon Richter
Possible Duplicates:
C/C++ Struct vs Class
What are POD types in C++?
Hi,
你好，
In the C++ In a Nutshell book, in chapter 6: classes, unders Access specifiers, mentioned the following:
在C++ In a Nutshell book，第 6 章： classes， unders Access specifiers，提到了以下内容：
In a class definition, the default access for members and base classes is private. In a struct definition, the default is public. That is the only difference between a class and a struct, although by convention, some programmers use struct only for POD classesand use class for all other classes.
在类定义中，成员和基类的默认访问权限是私有的。在 struct 定义中，默认值为 public。这是 class 和 struct 之间的唯一区别，尽管按照惯例，一些程序员仅将 struct 用于POD 类，而将 class 用于所有其他类。
My questions here are:
我的问题是：
- Isn't there another difference between classes and structs in that structs don't hold functions and just hold data?
- What are POD classes? And, what is meant by all other classes here? Are there then special classes?
- 类和结构之间是否还有另一个区别，即结构不保存函数而只保存数据？
- 什么是 POD 类？而且，这里的所有其他类是什么意思？那么有专门的班级吗？
Thanks.
谢谢。
回答by Simon Richter
The other difference is that
另一个区别是
template<class T> ...
is allowed, but
是允许的，但是
template<struct T> ...
is not.
不是。
回答by BlueMonkMN
You could prove to yourself that there is no other difference by trying to define a function in a struct. I remember even my college professor who was teaching about structs and classes in C++ was surprised to learn this (after being corrected by a student). I believe it, though. It was kind of amusing. The professor kept saying what the differences were and the student kept saying "actually you can do that in a struct too". Finally the prof. asked "OK, what is the difference" and the student informed him that the only difference was the default accessibility of members.
您可以通过尝试在结构中定义函数来向自己证明没有其他区别。我记得甚至我的大学教授在 C++ 中教授结构和类的时候也很惊讶（在被学生纠正之后）。不过我相信。这有点有趣。教授一直在说差异是什么，而学生一直在说“实际上你也可以在结构中做到这一点”。最后是教授。问“好的，有什么区别”，学生告诉他唯一的区别是成员的默认可访问性。
A quick Google search suggests that POD stands for "Plain Old Data".
快速谷歌搜索表明 POD 代表“Plain Old Data”。
回答by Sriram
POD classes are Plain-Old data classes that have only data members and nothing else. There are a few questions on stackoverflow about the same. Find one here.
POD 类是Plain-Old 数据类，只有数据成员，没有其他任何东西。stackoverflow 上也有一些类似的问题。在这里找到一个。
Also, you can have functions as members of structs in C++ but not in C. You need to have pointers to functions as members in structs in C.
此外，您可以将函数作为 C++ 中结构的成员，但不能在 C 中使用。您需要将函数指针作为 C 中结构中的成员。
回答by René Nyffenegger
Ok, POD means plain old data. That usually refers to structswithoutany methods because these types are then used to structure multiple data that belong together.
好的，POD 意味着普通的旧数据。这通常是指structs没有任何方法，因为这些类型随后用于构造属于一起的多个数据。
As for structs not having methods: I have seen more than once that a struct had methods, and I don't feel that this would be unnatural.
至于没有方法的结构体：我不止一次看到结构体有方法，我不觉得这会不自然。
回答by knivil
1) It is the only difference in C++.
1) 这是 C++ 中的唯一区别。
2) POD: plain old dataOther classes -> not POD
2) POD：普通旧数据其他类 -> 不是 POD
