问题描述
C ++ 11中变量的定义如下(第3/6节):
The definition of a variable in C++11 is as follows (§3/6):
因此,非静态数据成员引用不是变量.为什么需要这种区分?这里的理由是什么?
So a non-static data member reference is not a variable. Why is this distinction necessary? What's the rationale here?
推荐答案
这是我可以在C ++中声明变量的一种方法:
Here's one way I can declare a variable in C++:
int scientist = 7;
此声明(在本例中为定义)之后,我可以使用scientist
读取并设置其值,获取其地址等.这是另一种声明:-
After this declaration (and definition, in this case), I can use scientist
to read and set its value, take its address, etc. Here's another kind of declaration:-
class Cloud {
public:
static int cumulonimbus = -1;
};
这有点复杂,因为我必须将新变量称为Cloud::cumulonimbus
,但是我仍然可以读取和设置其值,因此显然它仍然是变量.这是另一种声明:-
This one is a bit more complicated, because I have to refer to the new variable as Cloud::cumulonimbus
, but I can still read and set its value, so it's still obviously a variable. Here's a yet different kind of declaration:-
class Chamber {
public:
int pot;
};
但是在此声明之后,没有一个名为pot
或Chamber::pot
的变量.实际上,根本没有新的变量.我已经声明了一个新类,并且稍后再声明该类的实例时,它将有一个名为pot
的成员,但是现在,什么都没有.
But after this declaration, there isn't a variable called pot
, or Chamber::pot
. In fact there's no new variable at all. I've declared a new class, and when I later declare an instance of that class it will have a member called pot
, but right now, nothing is called that.
类的非静态数据成员本身不会创建新变量,而只是帮助您定义类的属性.如果确实创建了一个新变量,则可以编写如下代码:
A non-static data member of class doesn't create a new variable itself, it just helps you to define the properties of the class. If it did create a new variable, you'd be able to write code like this:
class Chamber {
public:
int pot;
};
void f(bool b) {
if (b)
Chamber::pot = 2;
}
那甚至意味着什么?它会找到每个Chamber
实例并将其所有pot
设置为2吗?这是胡说八道.
What would that even mean? Would it find every instance of Chamber
and set all their pot
s to 2? It's a nonsense.
一个简短的脚注:这里的标准语言专门讨论引用,但是为了使示例更容易,我一直在使用非引用.希望您能看到这不会改变其原理.
A quick footnote: the language of the standard here is talking specifically about references, but to make the examples easier, I've been using non-references. I hope you can see this doesn't change the principle of it.
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