私人成员派生类

前面的课程我们遗传的，我们已经让所有的公共数据成员为了简化的例子。在这一节，我们将谈论在遗传过程访问说明符的作用，以及ascover的不同类型遗传可能在C++。

这一点，你见过的私人和公共接入说明符，它确定谁能访问类的成员。有快速的环境，公众成员可以上网的人。私有成员只能由同一个类的成员函数访问。注意，这意味着不能访问私人成员派生类。

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class Base
{
private:
int m_nPrivate; // can only be accessed by Base member functions (not derived classes)
public:
int m_nPublic; // can be accessed by anybody
};

当处理继承类，事情有点复杂。

第一，有三分之一的访问说明符，我们还谈论因为它是唯一有用的遗传背景。受保护的访问说明符限制访问同一个类的成员函数，或派生类。

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class Base
{
public:
int m_nPublic; // can be accessed by anybody
private:
int m_nPrivate; // can only be accessed by Base member functions (but not derived classes)
protected:
int m_nProtected; // can be accessed by Base member functions, or derived classes.
};

class Derived: public Base
{
public:
Derived()
{
// Derived's access to Base members is not influenced by the type of inheritance used,
// so the following is always true:

m_nPublic = 1; // allowed: can access public base members from derived class
m_nPrivate = 2; // not allowed: can not access private base members from derived class
m_nProtected = 3; // allowed: can access protected base members from derived class
}
};

int main()
{
Base cBase;
cBase.m_nPublic = 1; // allowed: can access public members from outside class
cBase.m_nPrivate = 2; // not allowed: can not access private members from outside class
cBase.m_nProtected = 3; // not allowed: can not access protected members from outside class
}