C++ 类（公共、私有和受保护）
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C++ classes (public, private, and protected)
提问by Simplicity
How can classes in C++ be declared public, private, or protected?
如何可以在C ++类中声明public，private或protected？
回答by templatetypedef
In C++ there is no notion of an entire class having an access specifier the way that there is in Java or C#. If a piece of code has visibility of a class, it can reference the name of that class and manipulate it. That said, there are a few restrictions on this. Just because you can reference a class doesn't mean you can instantiate it, for example, since the constructor might be marked private. Similarly, if the class is a nested class declared in another class's private or protected section, then the class won't be accessible outside from that class and its friends.
在 C++ 中，没有像在 Java 或 C# 中那样具有访问说明符的整个类的概念。如果一段代码具有类的可见性，它可以引用该类的名称并对其进行操作。也就是说，对此有一些限制。仅仅因为您可以引用一个类并不意味着您可以实例化它，例如，因为构造函数可能被标记为私有。类似地，如果该类是在另一个类的私有或受保护部分中声明的嵌套类，则该类将无法从该类及其朋友的外部访问。
回答by Benjamin Lindley
By nesting one class inside another:
通过将一个类嵌套在另一个类中：
class A
{
public:
class B {};
protected:
class C {};
private:
class D {};
};
回答by The Communist Duck
It depends if you mean members or inheritance. You can't have a 'private class', as such.
这取决于您是指成员还是继承。你不能有'private class', 这样的。
class Foo
{
public:
Foo() {} //public ctr
protected:
void Baz() //protected function
private:
void Bar() {} //private function
}
Or inheritance:
或者继承：
class Foo : public Bar
class Foo : protected Bar
class Foo : private Bar
回答by Edward Strange
You can implement "private classes" by simply not publishing their interface to clients.
您可以通过简单地不向客户端发布它们的接口来实现“私有类”。
I know of no way to create "protected classes".
我知道没有办法创建“受保护的类”。
