类的继承会首先寻找基类，若基类未实现，则会寻找派生类的函数

1. class继承，函数不继承

#include <stdio.h> class Base{public: Base(){} ~Base(){} int a; void setA() { a = 1; }}; class A:public Base{public: A(){} ~A(){} void setA() { a = 2; } }; class B:public Base{public: B(){} ~B(){} void setA() { a = 3; }}; int main(){ A *ax = new A(); B *bx = new B(); Base *aClass = ax; Base *bClass = bx; aClass->setA(); bClass->setA(); printf("a value of a %d\n", aClass->a); printf("a value of b %d\n", bClass->a); return 0;}

运行结果：

2. 函数和Class都继承

#include <stdio.h> class Base{public: Base(){} ~Base(){} int a; virtual void setA() { a = 1; }}; class A:public Base{public: A(){} ~A(){} virtual void setA() { a = 2; } }; class B:public Base{public: B(){} ~B(){} virtual void setA() { a = 3; }}; int main(){ A *ax = new A(); B *bx = new B(); Base *aClass = ax; Base *bClass = bx; aClass->setA(); bClass->setA(); printf("a value of a %d\n", aClass->a); printf("a value of b %d\n", bClass->a); return 0;}

运行结果：注意派生类中可以不写virtual，最好写上，以辨别是函数继承

若将2中基类的函数写为纯虚函数，运行的结果一样，但是如果基类是纯虚函数，派生类必须实现相应的函数。

class Base{public: Base(){} ~Base(){} int a; virtual void setA()=0; };

3. 类A中不有函数，则继承自基类

class A:public Base{public: A(){} ~A(){} };

结果为：

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