C++继承：public继承、protected继承、private继承

子类在类外只能访问 公有继承来的 父类的公有成员变量和公有成员函数
子类在类内能够访问 继承过来后属性为公有或保护的 父类的成员变量和成员函数

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提示：可以利用下方文件目录跳转到三种继承的具体实现代码

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结论

子类在类外只能访问 公有继承来的 父类的公有成员变量和公有成员函数
子类在类内能够访问 继承过来后属性为公有或保护的 父类的成员变量和成员函数

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一、公有继承

1.子类在类内访问父类的成员变量和成员函数

#include 
using namespace std;
class A {
public:
 string variablePublic = "父类公有成员变量";
 void function_Public();
protected:
 string variableProtected = "父类保护成员变量";
 void function_Protected();
private:
 string variablePrivate = "父类私有成员变量";
 void function_Private();
};
void A::function_Public() {
 cout << "父类公有成员函数" << endl;
}
void A::function_Protected() {
 cout << "父类保护成员函数" << endl;
}
void A::function_Private() {
 cout << "父类私有成员函数" << endl;
}
class B:public A{
public:
 void show();
};
void B::show() {
 cout << variablePublic << endl;
 cout << variableProtected << endl;
 //cout << variablePrivate << endl;
 function_Public();
 function_Protected();
 //function_Private();
}
int main() {
 B b;
 b.show();
 return 0;
}

2.子类在类外访问父类的成员变量和成员函数

#include 
using namespace std;
class A {
public:
 string variablePublic = "父类公有成员变量";
 void function_Public();
protected:
 string variableProtected = "父类保护成员变量";
 void function_Protected();
private:
 string variablePrivate = "父类私有成员变量";
 void function_Private();
};
void A::function_Public() {
 cout << "父类公有成员函数" << endl;
}
void A::function_Protected() {
 cout << "父类保护成员函数" << endl;
}
void A::function_Private() {
 cout << "父类私有成员函数" << endl;
}
class B:public A{
public:
 void show();
};
void B::show() {
 cout << variablePublic << endl;
 cout << variableProtected << endl;
 //cout << variablePrivate << endl;
 function_Public();
 function_Protected();
 //function_Private();
}
int main() {
 B b;
 cout << b.variablePublic<<endl;
 //cout << b.variableProtected << endl;
 //cout << b.variablePrivate << endl;
 b.function_Public();
 //b.function_Protected();
 //b.function_Private();
 return 0;
}

示例：pandas 是基于NumPy 的一种工具，该工具是为了解决数据分析任务而创建的。

二、保护继承

1.子类在类内访问父类的成员变量和成员函数

#include 
using namespace std;
class A {
public:
 string variablePublic = "父类公有成员变量";
 void function_Public();
protected:
 string variableProtected = "父类保护成员变量";
 void function_Protected();
private:
 string variablePrivate = "父类私有成员变量";
 void function_Private();
};
void A::function_Public() {
 cout << "父类公有成员函数" << endl;
}
void A::function_Protected() {
 cout << "父类保护成员函数" << endl;
}
void A::function_Private() {
 cout << "父类私有成员函数" << endl;
}
class B:protected A{
public:
 void show();
};
void B::show() {
 cout << variablePublic << endl;
 cout << variableProtected << endl;
 //cout << variablePrivate << endl; //不可访问
 function_Public();
 function_Protected();
 //function_Private();  //不可访问
}
int main() {
 B b;
 b.show();
 return 0;
}

2.子类在类外访问父类的成员变量和成员函数

#include 
using namespace std;
class A {
public:
 string variablePublic = "父类公有成员变量";
 void function_Public();
protected:
 string variableProtected = "父类保护成员变量";
 void function_Protected();
private:
 string variablePrivate = "父类私有成员变量";
 void function_Private();
};
void A::function_Public() {
 cout << "父类公有成员函数" << endl;
}
void A::function_Protected() {
 cout << "父类保护成员函数" << endl;
}
void A::function_Private() {
 cout << "父类私有成员函数" << endl;
}
class B :protected A {
public:
 void show();
};
void B::show() {
 cout << variablePublic << endl;
 cout << variableProtected << endl;
 //cout << variablePrivate << endl;
 function_Public();
 function_Protected();
 //function_Private();
}
int main() {
 B b;
 //cout << b.variablePublic << endl;     //不可访问
 //cout << b.variableProtected << endl;  //不可访问
 //cout << b.variablePrivate << endl;    //不可访问
 //b.function_Public();        //不可访问
 //b.function_Protected();               //不可访问
 //b.function_Private();                 //不可访问
 return 0;//不可访问
}

没有输出

三、私有继承

1.子类在类内访问父类的成员变量和成员函数

#include 
using namespace std;
class A {
public:
 string variablePublic = "父类公有成员变量";
 void function_Public();
protected:
 string variableProtected = "父类保护成员变量";
 void function_Protected();
private:
 string variablePrivate = "父类私有成员变量";
 void function_Private();
};
void A::function_Public() {
 cout << "父类公有成员函数" << endl;
}
void A::function_Protected() {
 cout << "父类保护成员函数" << endl;
}
void A::function_Private() {
 cout << "父类私有成员函数" << endl;
}
class B :private A {
public:
 void show();
};
void B::show() {
 cout << variablePublic << endl;
 cout << variableProtected << endl;
 //cout << variablePrivate << endl; //不可访问
 function_Public();
 function_Protected();
 //function_Private();              //不可访问
}
int main() {
 B b;
 b.show();
 return 0;//不可访问
}

2.子类在类外访问父类的成员变量和成员函数

#include 
using namespace std;
class A {
public:
 string variablePublic = "父类公有成员变量";
 void function_Public();
protected:
 string variableProtected = "父类保护成员变量";
 void function_Protected();
private:
 string variablePrivate = "父类私有成员变量";
 void function_Private();
};
void A::function_Public() {
 cout << "父类公有成员函数" << endl;
}
void A::function_Protected() {
 cout << "父类保护成员函数" << endl;
}
void A::function_Private() {
 cout << "父类私有成员函数" << endl;
}
class B :private A {
public:
 void show();
};
void B::show() {
 cout << variablePublic << endl;
 cout << variableProtected << endl;
 //cout << variablePrivate << endl; //不可访问
 function_Public();
 function_Protected();
 //function_Private();              //不可访问
}
int main() {
 B b;
 //cout << b.variablepublic << endl;     //不可访问
 //cout << b.variableprotected << endl;  //不可访问
 //cout << b.variableprivate << endl;    //不可访问
 //b.function_public();        //不可访问
 //b.function_protected();               //不可访问
 //b.function_private();                 //不可访问
 return 0;//不可访问
}

没有输出